A field-based Intercomparison study of a commercial Differential Optical Absorption Spectroscopy (DOAS) instrument (OPSIS AB, Sweden) and different point-sample monitoring techniques (PM, based on an air monitoring st...A field-based Intercomparison study of a commercial Differential Optical Absorption Spectroscopy (DOAS) instrument (OPSIS AB, Sweden) and different point-sample monitoring techniques (PM, based on an air monitoring station, an air monitoring vehicle, and various chemical methods) was conducted in Beijing from October 1999 to January 2000. The mixing ratios of six trace gases including NO, NO2, SO2, O3, benzene, and toluene were monitored continuously during the four months. A good agreement between the DOAS and PM data was found for NO2 and SO2. However, the concentrations of benzene, toluene, and NO obtained by DOAS were significantly lower than those measured by the point monitors. The ozone levels monitored by the DOAS were generally higher than those measured by point monitors. These results may be attributed to a strong vertical gradient of the NO-O3-NO2 system and of the aromatics at the measurement site. Since the exact data evaluation algorithm is not revealed by the manufacturer of the DOAS system, the error in the DOAS analysis can also not be excluded.展开更多
Sea surface winds are of great significance in scientific research. In the last few years,three series of scatterometers were launched to measure these winds,including the Advanced Scatterometer(ASCAT) aboard Meteorol...Sea surface winds are of great significance in scientific research. In the last few years,three series of scatterometers were launched to measure these winds,including the Advanced Scatterometer(ASCAT) aboard Meteorological Operational Satellite A(Met Op-A) and Met Op-B,Oceansat-2 Scatterometer(OSCAT),and HY-2A Scatterometer(HY-2A SCAT). Based on buoy wind data,validation and intercomparison of these scatterometers were performed. Scatterometer-derived wind and buoy wind data were collected only if the spatial difference was less than 0.1 degree and temporal difference less than 5 min. After discarding wind direction data outside five times the standard deviation,ASCAT wind products showed high accuracy in both wind speed and direction,with root-mean-square error(RMSE) 0.86 m/s and 17.97 degrees,respectively. HY-2A SCAT nearly meets the mission requirement,with RMSE for wind speed 1.23 m/s and 22.85 degrees for wind direction. OSCAT had poor performance when compared with the others. RMSE for wind speed was 1.54 m/s and 39.86 degrees for wind direction,which greatly exceeds the mission requirement of 20 degrees. In addition,the RMSE for wind direction shows a high-low pattern on buoy wind speed. However,a wind speed range from 14 to 15 m/s was found to be abnormal,and the reason remains unclear. There was no systematic dependency of both wind speed and direction residuals on buoy wind speed and cross-track location of the wind vector cells across the entire range. No seasonal variation was found for any scatterometer.展开更多
Three numerical oceanic circulation models: POM(Princeton ocean model), MICOM(Miami isopycnal coordinates ocean model) and GFDL model, which adopt sigma coordinate, isopycnal coordinate and depth coordinate respectiv...Three numerical oceanic circulation models: POM(Princeton ocean model), MICOM(Miami isopycnal coordinates ocean model) and GFDL model, which adopt sigma coordinate, isopycnal coordinate and depth coordinate respectively, are used in the South China Sea(SCS) circulation modeling. Model domain has the same topography, grid resolution, initial conditions and surface boundary conditions. The maximum ocean depth is set as 1 000 m. Grid resolution is 0.5o×0.5o.Initial conditions are supplied by climatological temperature and salinity data in January. Climatological wind stress, surface temperature and salinity are used as surface forcing. Lateral boundaries take enclosed boundary conditions artificially. Focusing on the common point of different ocean circulation models, the circulation pattern in winter and summer, sea surface height in the northern SCS, seasonal cycle of the mixed layer thickness in the southern SCS, barotropic stream function in winter are selected to carry out intercomparison. In winter, a strong cyclonic gyre occupies the whole SCS. In summer, a strong anticyclonic gyre occupies the southern SCS and a weak cyclonic gyre occupies the northern SCS. The thickness of the mixed layer shows bimodal features in the southern SCS. Sea surface height anomaly(SSHA) in the northern SCS has an eastward propagating feature, in agreement with the remote sensing observation. Barotropic stream functions indicate that the circulation of the upper ocean is mainly forced by inputting of wind stress curl under closed boundary conditions. In addition, three models also show distinct differences. The basin-scale circulation from MICOM is distinct. Output of POM has more mesoscale eddies than others. GFDL model seems good at simulating westward intensification.展开更多
Regional coupled modeling is one of the frontiers of regional climate modeling,but intercomparison has not been well coordinated.In this study,a community regional climate model,WRF4,with a resolution of 15 km,was cou...Regional coupled modeling is one of the frontiers of regional climate modeling,but intercomparison has not been well coordinated.In this study,a community regional climate model,WRF4,with a resolution of 15 km,was coupled with a high-resolution(0.1°)North Pacific Ocean model(LICOM_np).The performance of the regional coupled model,WRF4_LICOM,was compared to that of another regional coupled model,RegCM4_LICOM,which was a coupling of version 4 of the Regional Climate Model(RegCM4)with LICOM_np.The analysis focused on the 2005 western North Pacific summer monsoon rainfall.The results showed that the regional coupled models with either RegCM4 or WRF4 as their atmospheric model component simulated the broad features over the WNP reasonably well.Quantitative intercomparison of the regional coupled simulations exhibited different biases for different climate variables.RegCM4_LICOM exhibited smaller biases in its simulation of the averaged June–July–August SST and rainfall,while WRF4_LICOM better captured the tropical cyclone(TC)intensity,the percentage contributions of rainfall induced by TCs to the total rainfall,and the diurnal cycle of rainfall and stratiform percentages,especially over land areas.The different behaviors in rainfall simulated by the two models were partly ascribed to the behaviors in the simulated western North Pacific subtropical high(WNPSH).The stronger(weaker)WNPSH in WRF4_LICOM(RegCM4_LICOM)was driven by overestimated(underestimated)diabatic heating,which peaked at approximately 450 hPa over the region around the Philippines in association with different condensation–radiation processes.Coupling of WRF4 with LIOCM is a crucial step towards the development of the next generation of regional earth system models at the Chinese Academy of Sciences.展开更多
The time-mean and interannual variability of the interface between the Indian summer monsoon and East Asian summer monsoon （IIE） was assessed using both Max-Planck-Institute Earth System Model （MPI-ESM） and ECHAM5...The time-mean and interannual variability of the interface between the Indian summer monsoon and East Asian summer monsoon （IIE） was assessed using both Max-Planck-Institute Earth System Model （MPI-ESM） and ECHAM5/MPI-OM and by calculating diagnostics and skill metrics around the IIE area. Progress has been made in modeling these aspects by moving from ECHAM5/MPI-OM to MPI-ESM. MPI-ESM is more skillful than ECHAM5/MPI-OM in modeling the time-mean state and the extreme condition of the IIE. Though simulation of the interannual variability significantly deviates to some extent in both MPI-ESM and ECHAM5/MPI-OM, MPI-ESM-LR shows better skill in reflecting the relationship among sea surface temperature anomalies over the Pacific, circulation anomalies over East Asia, and liE variability. The temperature becomes warmer under the RCP2.6 and RCP8.5 scenarios in comparison with the historical experiments, but the position of the liE and the key physical process in relation to the IIE variability almost remains the same, suggesting that the Indian summer monsoon tends to change in phase with the East Asian summer monsoon under each RCP scenario. The relatively realistic description of the physical processes modulated by terrain in MPI-ESM may be one of the most important reasons why MPI-ESM performs better in simulating the liE.展开更多
Version 4(v4) of the Extended Reconstructed Sea Surface Temperature(ERSST) dataset is compared with its precedent, the widely used version 3b(v3b). The essential upgrades applied to v4 lead to remarkable differences i...Version 4(v4) of the Extended Reconstructed Sea Surface Temperature(ERSST) dataset is compared with its precedent, the widely used version 3b(v3b). The essential upgrades applied to v4 lead to remarkable differences in the characteristics of the sea surface temperature(SST) anomaly(SSTa) in both the temporal and spatial domains. First, the largest discrepancy of the global mean SSTa values around the 1940 s is due to ship-observation corrections made to reconcile observations from buckets and engine intake thermometers. Second, differences in global and regional mean SSTa values between v4 and v3b exhibit a downward trend(around-0.032℃ per decade) before the 1940s, an upward trend(around 0.014℃ per decade) during the period of 1950–2015, interdecadal oscillation with one peak around the 1980s, and two troughs during the 1960s and 2000s, respectively. This does not derive from treatments of the polar or the other data-void regions, since the difference of the SSTa does not share the common features. Third, the spatial pattern of the ENSO-related variability of v4 exhibits a wider but weaker cold tongue in the tropical region of the Pacific Ocean compared with that of v3b, which could be attributed to differences in gap-filling assumptions since the latter features satellite observations whereas the former features in situ ones. This intercomparison confirms that the structural uncertainty arising from underlying assumptions on the treatment of diverse SST observations even in the same SST product family is the main source of significant SST differences in the temporal domain. Why this uncertainty introduces artificial decadal oscillations remains unknown.展开更多
Spatiotemporal variations of ozone(O_(3))taken from the Copernicus Atmosphere Monitoring Service(CAMS)and the second Modern-Era Retrospective Analysis for Research and Applications(MERRA-2)were intercompared and evalu...Spatiotemporal variations of ozone(O_(3))taken from the Copernicus Atmosphere Monitoring Service(CAMS)and the second Modern-Era Retrospective Analysis for Research and Applications(MERRA-2)were intercompared and evaluated with ground and ozone-sonde observations over China in 2018 and 2019.Intercomparison of the surface ozone from CAMS and MERRA-2 reanalysis showed significant negative bias(CAMS minus MERRA-2,same below)at Tibetan Plateau of up to 80μg/m^(3),and the average R^(2)was about 0.6 across China.Evaluated with the ground observations from China National Environmental Monitoring Center(CNEMC),we found that CAMS and MERRA-2 reanalysis were capable of capturing the key patterns of monthly and diurnal variations of surface ozone over China except for the western region,and MERRA-2 overestimated the observations compared to CAMS.Vertically,the CAMS profiles overestimated the ozone-sonde from the World Ozone and Ultraviolet Radiation Data Center(WOUDC)above 200 h Pa with the magnitude reaching up to 150μg/m3,while little bias was found between the reanalysis and observations below 200 h Pa.Intercomparison drawn from the vertical distribution between CAMS and MERRA-2 reanalysis showed that the negative bias appeared throughout the troposphere over China,while the positive bias emerged in the upper troposphere and lower stratosphere(UTLS)with high order of magnitude exceeding 100μg/m^(3),indicating large uncertainties at higher altitudes.In summary,we concluded that CAMS reanalysis showed better agreement with the observations in contrast to MERRA-2,and the large discrepancy especially at higher altitudes between these two reanalysis datasets could not be ignored.展开更多
A model intercomparison in terms of surface air temperature annual cycle amplitude-phase characteristics (SAT AC APC) is performed. The models included in the intercomparison belong to two groups: five atmospheric mod...A model intercomparison in terms of surface air temperature annual cycle amplitude-phase characteristics (SAT AC APC) is performed. The models included in the intercomparison belong to two groups: five atmospheric models with prescribed sea surface temperature and sea ice cover and four coupled models forced by the atmospheric abundances of anthropogenic constituents (in total six coupled model simulations). Over land, the models, simulating higher than observed time averaged SAT, also tend to simulate smaller than observed amplitude of its annual and semiannual harmonics and (outside the Tropics) later-than-observed spring and autumn moments. The models with larger (smaller) time averaged amplitudes of annual and semiannual harmonics also tend to simulate larger (smaller) interannual standard deviations. Over the oceans, the coupled models with larger interannual standard deviations of annual mean SAT tend to simulate larger interannual standard deviations of both annual and semiannual SAT harmonics amplitudes. Most model errors are located in the belts 60°–70°N and 60°–70°S and over Antarctica. These errors are larger for those coupled models which do not employ dynamical modules for sea ice. No systematic differences are found in the simulated time averaged fields of the surface air temperature annual cycle characteristics for atmospheric models on one hand and for the coupled models on the other. But the coupled models generally simulate interannual variability of SAT AC APC better than the atmospheric models (which tend to underestimate it). For the coupled models, the results are not very sensitive to the choice of the particular scenario of anthropogenic forcing. There is a strong linear positive relationship between the model simulated time averaged semiannual SAT harmonics amplitude and interannual standard deviation of annual mean SAT. It is stronger over the tropical oceans and is weaker in the extratropics. In the tropical oceanic areas, it is stronger for the coupled than for the atmospheric models.展开更多
This analysis of the multi-model aerosol optical depth (AOD) in eastern China using the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) datasets shows that the global models underestimate the ...This analysis of the multi-model aerosol optical depth (AOD) in eastern China using the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) datasets shows that the global models underestimate the AOD by 33% and 44% in southern and northern China, respectively, and decrease the relative humidity (RH) of the air in the surface layer to 71%–80%, which is less than the RH of 77%–92% in reanalysis meteorological datasets. This indicates that the low biases in the RH partially account for the errors in the AOD. The AOD is recalculated based on the model aerosol concentrations and the reanalysis humidity data. Improving the mean value of the RH increases the multi-model annual mean AOD by 45% in southern China and by 33% in June–August in northern China. This method of improving the AOD is successful in most of the ACCMIP models, but it is unlikely to be successful in GISS-E2-R, in which the plot of its AOD efficiency against RH strongly deviates from the rest of the models. The effect of the improvement in the modeled RH on the AOD depends on the concentration of aerosols. The shape error in the frequency distribution of the RH is likely to be more important than the error in the mean value of the RH, but this requires further research.展开更多
Within the context of the Belt and Road Initiative(BRI)and the China-Myanmar Economic Corridor(CMEC),the Dulong-Ir-rawaddy(Ayeyarwady)River,an international river among China,India and Myanmar,plays a significant role...Within the context of the Belt and Road Initiative(BRI)and the China-Myanmar Economic Corridor(CMEC),the Dulong-Ir-rawaddy(Ayeyarwady)River,an international river among China,India and Myanmar,plays a significant role as both a valuable hydro-power resource and an essential ecological passageway.However,the water resources and security exhibit a high degree of vulnerabil-ity to climate change impacts.This research evaluates climate impacts on the hydrology of the Dulong-Irrawaddy River Basin(DIRB)by using a physical-based hydrologic model.We crafted future climate scenarios using the three latest global climate models(GCMs)from Coupled Model Intercomparison Project 6(CMIP6)under two shared socioeconomic pathways(SSP2-4.5 and SSP5-8.5)for the near(2025-2049),mid(2050-2074),and far future(2075-2099).The regional model using MIKE SHE based on historical hydrologic processes was developed to further project future streamflow,demonstrating reliable performance in streamflow simulations with a val-idation Nash-Sutcliffe Efficiency(NSE)of 0.72.Results showed that climate change projections showed increases in the annual precip-itation and potential evapotranspiration(PET),with precipitation increasing by 11.3%and 26.1%,and PET increasing by 3.2%and 4.9%,respectively,by the end of the century under SSP2-4.5 and SSP5-8.5.These changes are projected to result in increased annual streamflow at all stations,notably at the basin’s outlet(Pyay station)compared to the baseline period(with an increase of 16.1%and 37.0%at the end of the 21st century under SSP2-4.5 and SSP5-8.5,respectively).Seasonal analysis for Pyay station forecasts an in-crease in dry-season streamflow by 31.3%-48.9%and 22.5%-76.3%under SSP2-4.5 and SSP5-8.5,respectively,and an increase in wet-season streamflow by 5.8%-12.6%and 2.8%-33.3%,respectively.Moreover,the magnitude and frequency of flood events are pre-dicted to escalate,potentially impacting hydropower production and food security significantly.This research outlines the hydrological response to future climate change during the 21st century and offers a scientific basis for the water resource management strategies by decision-makers.展开更多
Global warming induced by increased CO_(2) has caused marked changes in the ocean.Previous estimates of ocean salinity change in response to global warming have considerable ambiguity,largely attributable to the diver...Global warming induced by increased CO_(2) has caused marked changes in the ocean.Previous estimates of ocean salinity change in response to global warming have considerable ambiguity,largely attributable to the diverse sensitivities of surface fluxes.This study utilizes data from the Flux-Anomaly-Forced Model Intercomparison Project to investigate how ocean salinity responds to perturbations of surface fluxes.The findings indicate the emergence of a sea surface salinity(SSS)dipole pattern predominantly in the North Atlantic and Pacific fresh pools,driven by surface flux perturbations.This results in an intensification of the“salty gets saltier and fresh gets fresher”SSS pattern across the global ocean.The spatial pattern amplification(PA)of SSS under global warming is estimated to be approximately 11.5%,with surface water flux perturbations being the most significant contributor to salinity PA,accounting for 8.1% of the change after 70 years in experiments since pre-industrial control(piControl).Notably,the zonal-depth distribution of salinity in the upper ocean exhibits lighter seawater above the denser water,with bowed isopycnals in the upper 400 m.This stable stratification inhibits vertical mixing of salinity and temperature.In response to the flux perturbations,there is a strong positive feedback due to consequent freshening.It is hypothesized that under global warming,an SSS amplification of 7.2%/℃ and a mixed-layer depth amplification of 12.5%/℃ will occur in the global ocean.It suggests that the salinity effect can exert a more stable ocean to hinder the downward transfer of heat,which provides positive feedback to future global warming.展开更多
The development of coupled earth/climate system models in China over the past 20 years is reviewed, including a comparison with other international models that participated in the Coupled Model Intercom- parison Proje...The development of coupled earth/climate system models in China over the past 20 years is reviewed, including a comparison with other international models that participated in the Coupled Model Intercom- parison Project （CMIP） from phase 1 （CMIP1） to phase 4 （CMIP4）. The Chinese contribution to CMIP is summarized, and the major achievements from CMIP1 to CMIP3 are listed as a reference for assessing the strengths and weaknesses of Chinese models. After a description of CMIP5 experiments, the five Chinese models that participated in CMIP5 are then introduced. Furthermore, following a review of the current status of international model development, both the challenges and opportunities for the Chinese climate modeling community are discussed. The development of high-resolution climate models, earth system mod- els, and improvements in atmospheric and oceanic general circulation models, which are core components of earth/climate system models, are highlighted. To guarantee the sustainable development of climate system models in China, the need for national-level coordination is discussed, along with a list of the main compo- nents and supporting elements identified by the US National Strategy for Advancing Climate Modeling.展开更多
The AHI-FSA(Advanced Himawari Imager-Fire Surveillance Algorithm)is a recently developed algorithm designed to support wildfire surveillance and mapping using the geostationary Himawari-8 satellite.At present,the AHI-...The AHI-FSA(Advanced Himawari Imager-Fire Surveillance Algorithm)is a recently developed algorithm designed to support wildfire surveillance and mapping using the geostationary Himawari-8 satellite.At present,the AHI-FSA algorithm has only been tested on a number of case study fires in Western Australia.Initial results demonstrate potential as a wildfire surveillance algorithm providing high frequency(every 10 minutes),multi-resolution fire-line detections.This paper intercompares AHI-FSA across the Northern Territory of Australia(1.4 million km2)over a ten-day period with the well-established fire products from LEO(Low Earth Orbiting)satellites:MODIS(Moderate Resolution Imaging Spectroradiometer)and VIIRS(Visible Infrared Imaging Radiometer Suite).This paper also discusses the difficulties and solutions when comparing high temporal frequency fire products with existing low temporal resolution LEO satellite products.The results indicate that the multi-resolution approach developed for AHI-FSA is successful in mapping fire activity at 500 m.When compared to the MODIS,daily AHIFSA omission error was only 7%.High temporal frequency data also results in AHI-FSA observing fires,at times,three hours before the MODIS overpass with much-enhanced detail on fire movement.展开更多
In recent years,algorithms have been developed to derive land surface temperature(LST)from geostationary and polar satellite systems.However,few works have addressed the intercomparison between Geostationary Operation...In recent years,algorithms have been developed to derive land surface temperature(LST)from geostationary and polar satellite systems.However,few works have addressed the intercomparison between Geostationary Operational Environmental Satellites(GOES)and the available suite of polar sensors.In this study,differences in LSTs between GOES and MODerate resolution Imaging Spectroradiometer(MODIS)have been compared and also evaluated against ground observations.Due to the lack of split-window(SW)channels in the GOES M(12)-Q era,a dual-window algorithm using a mid-infrared 3.9µm channel is compared with traditional SW algorithm.It is found that the differences in LST between different platforms are bigger during daytime than those during nighttime.During daytime,LSTs from GOES with the dualwindow algorithm are warmer than MODIS LSTs,while LSTs from the SW algorithm are close to MODIS LSTs.The difference during daytime is found to be related to anisotropy in satellite viewing geometry,and land surface properties,such as vegetation cover and especially surface emissivity at middle infrared(MIR)channel.When evaluated against ground observations,the standard deviation(precision)error(2.35 K)from the dual window algorithm is worse than that(1.83 K)from the SW algorithm,indicating the lack of split-window channel in the GOES M(12)-Q era may degrade the performance of LST retrievals.展开更多
We characterize the agreement and disagreement of four publically available burned products(Fire CCI,Copernicus Burnt Area,MODIS MCD45A1,and MODIS MCD64A1)at a finer spatial and temporal scale than previous assessment...We characterize the agreement and disagreement of four publically available burned products(Fire CCI,Copernicus Burnt Area,MODIS MCD45A1,and MODIS MCD64A1)at a finer spatial and temporal scale than previous assessments using a grid of three-dimensional cells defined both in space and in time.Our analysis,conducted using seven years of data(2005–2011),shows that estimates of burned area vary greatly between products in terms of total area burned,the location of burning,and the timing of the burning.We use regional and monthly units for analysis to provide insight into the variation between products that can be lost when considering products yearly and/or globally.Comparison with independent,contemporaneous MODIS active fire observations provides one indication of which products most reasonably capture the burning regime.Our results have implications for the use of global burned area products in fire ecology,management and emissions applications.展开更多
This paper evaluates a representation of winter stratospheric circulation in the Antarctic that is based on CRA-40, a 40-year global reanalysis dataset released by the China Meteorological Administration, and compares...This paper evaluates a representation of winter stratospheric circulation in the Antarctic that is based on CRA-40, a 40-year global reanalysis dataset released by the China Meteorological Administration, and compares it with representations based on two other state-of-the-art reanalysis datasets: the fifth-generation atmospheric reanalysis provided by the European Centre for Medium-Range Weather Forecasts(ERA-5) and the Modern-Era Retrospective analysis for Research and Applications, version 2(MERRA-2). In terms of climatology, we find that CRA-40 portrays a stronger and colder polar vortex in the middle and lower stratosphere than ERA-5, but a weaker and warmer one than MERRA-2. However, disagreement among the three reanalyses is confined mainly to the period before1999, and is largely reduced after that time. On the interannual timescale, portrayals of the intensity and area of the 10-hPa polar vortex are quite consistent among the three reanalyses, with correlation coefficients greater than 0.9 between each pair of reanalyses. In addition, the central dates of most sudden stratospheric deceleration(SSD) events at 10 hPa in the three reanalyses differ by less than one day, indicating that CRA-40 is also highly consistent with the other two reanalysis datasets regarding daily evolution. Our analyses suggest that CRA-40 performs comparably to ERA-5 and MERRA-2 in characterizing winter circulation in the Antarctic middle and lower stratosphere.展开更多
It is fundamental and useful to investigate how deep learning forecasting models(DLMs)perform compared to operational oceanography forecast systems(OFSs).However,few studies have intercompared their performances using...It is fundamental and useful to investigate how deep learning forecasting models(DLMs)perform compared to operational oceanography forecast systems(OFSs).However,few studies have intercompared their performances using an identical reference.In this study,three physically reasonable DLMs are implemented for the forecasting of the sea surface temperature(SST),sea level anomaly(SLA),and sea surface velocity in the South China Sea.The DLMs are validated against both the testing dataset and the“OceanPredict”Class 4 dataset.Results show that the DLMs'RMSEs against the latter increase by 44%,245%,302%,and 109%for SST,SLA,current speed,and direction,respectively,compared to those against the former.Therefore,different references have significant influences on the validation,and it is necessary to use an identical and independent reference to intercompare the DLMs and OFSs.Against the Class 4 dataset,the DLMs present significantly better performance for SLA than the OFSs,and slightly better performances for other variables.The error patterns of the DLMs and OFSs show a high degree of similarity,which is reasonable from the viewpoint of predictability,facilitating further applications of the DLMs.For extreme events,the DLMs and OFSs both present large but similar forecast errors for SLA and current speed,while the DLMs are likely to give larger errors for SST and current direction.This study provides an evaluation of the forecast skills of commonly used DLMs and provides an example to objectively intercompare different DLMs.展开更多
文摘A field-based Intercomparison study of a commercial Differential Optical Absorption Spectroscopy (DOAS) instrument (OPSIS AB, Sweden) and different point-sample monitoring techniques (PM, based on an air monitoring station, an air monitoring vehicle, and various chemical methods) was conducted in Beijing from October 1999 to January 2000. The mixing ratios of six trace gases including NO, NO2, SO2, O3, benzene, and toluene were monitored continuously during the four months. A good agreement between the DOAS and PM data was found for NO2 and SO2. However, the concentrations of benzene, toluene, and NO obtained by DOAS were significantly lower than those measured by the point monitors. The ozone levels monitored by the DOAS were generally higher than those measured by point monitors. These results may be attributed to a strong vertical gradient of the NO-O3-NO2 system and of the aromatics at the measurement site. Since the exact data evaluation algorithm is not revealed by the manufacturer of the DOAS system, the error in the DOAS analysis can also not be excluded.
基金Supported by the National Natural Science Foundation of China(Nos.U1406404,41331172,61361136001)the National High Technology Research and Development Program of China(863 Program)(No.2013AA09A505)
文摘Sea surface winds are of great significance in scientific research. In the last few years,three series of scatterometers were launched to measure these winds,including the Advanced Scatterometer(ASCAT) aboard Meteorological Operational Satellite A(Met Op-A) and Met Op-B,Oceansat-2 Scatterometer(OSCAT),and HY-2A Scatterometer(HY-2A SCAT). Based on buoy wind data,validation and intercomparison of these scatterometers were performed. Scatterometer-derived wind and buoy wind data were collected only if the spatial difference was less than 0.1 degree and temporal difference less than 5 min. After discarding wind direction data outside five times the standard deviation,ASCAT wind products showed high accuracy in both wind speed and direction,with root-mean-square error(RMSE) 0.86 m/s and 17.97 degrees,respectively. HY-2A SCAT nearly meets the mission requirement,with RMSE for wind speed 1.23 m/s and 22.85 degrees for wind direction. OSCAT had poor performance when compared with the others. RMSE for wind speed was 1.54 m/s and 39.86 degrees for wind direction,which greatly exceeds the mission requirement of 20 degrees. In addition,the RMSE for wind direction shows a high-low pattern on buoy wind speed. However,a wind speed range from 14 to 15 m/s was found to be abnormal,and the reason remains unclear. There was no systematic dependency of both wind speed and direction residuals on buoy wind speed and cross-track location of the wind vector cells across the entire range. No seasonal variation was found for any scatterometer.
基金This work was supported by the MOST“863”Program of China under contract No.2002AA639250the Ma-jor State Basic Research Program of China under con-tract No.S5 1999043806 and G1999043810.
文摘Three numerical oceanic circulation models: POM(Princeton ocean model), MICOM(Miami isopycnal coordinates ocean model) and GFDL model, which adopt sigma coordinate, isopycnal coordinate and depth coordinate respectively, are used in the South China Sea(SCS) circulation modeling. Model domain has the same topography, grid resolution, initial conditions and surface boundary conditions. The maximum ocean depth is set as 1 000 m. Grid resolution is 0.5o×0.5o.Initial conditions are supplied by climatological temperature and salinity data in January. Climatological wind stress, surface temperature and salinity are used as surface forcing. Lateral boundaries take enclosed boundary conditions artificially. Focusing on the common point of different ocean circulation models, the circulation pattern in winter and summer, sea surface height in the northern SCS, seasonal cycle of the mixed layer thickness in the southern SCS, barotropic stream function in winter are selected to carry out intercomparison. In winter, a strong cyclonic gyre occupies the whole SCS. In summer, a strong anticyclonic gyre occupies the southern SCS and a weak cyclonic gyre occupies the northern SCS. The thickness of the mixed layer shows bimodal features in the southern SCS. Sea surface height anomaly(SSHA) in the northern SCS has an eastward propagating feature, in agreement with the remote sensing observation. Barotropic stream functions indicate that the circulation of the upper ocean is mainly forced by inputting of wind stress curl under closed boundary conditions. In addition, three models also show distinct differences. The basin-scale circulation from MICOM is distinct. Output of POM has more mesoscale eddies than others. GFDL model seems good at simulating westward intensification.
基金jointly supported by the National Key Research and Development Program of China(Grant No.2018YFA0606003)the National Natural Science Foundation of China(Grant Nos.41875132 and 41575105)the Jiangsu Collaborative Innovation Center for Climate Change。
文摘Regional coupled modeling is one of the frontiers of regional climate modeling,but intercomparison has not been well coordinated.In this study,a community regional climate model,WRF4,with a resolution of 15 km,was coupled with a high-resolution(0.1°)North Pacific Ocean model(LICOM_np).The performance of the regional coupled model,WRF4_LICOM,was compared to that of another regional coupled model,RegCM4_LICOM,which was a coupling of version 4 of the Regional Climate Model(RegCM4)with LICOM_np.The analysis focused on the 2005 western North Pacific summer monsoon rainfall.The results showed that the regional coupled models with either RegCM4 or WRF4 as their atmospheric model component simulated the broad features over the WNP reasonably well.Quantitative intercomparison of the regional coupled simulations exhibited different biases for different climate variables.RegCM4_LICOM exhibited smaller biases in its simulation of the averaged June–July–August SST and rainfall,while WRF4_LICOM better captured the tropical cyclone(TC)intensity,the percentage contributions of rainfall induced by TCs to the total rainfall,and the diurnal cycle of rainfall and stratiform percentages,especially over land areas.The different behaviors in rainfall simulated by the two models were partly ascribed to the behaviors in the simulated western North Pacific subtropical high(WNPSH).The stronger(weaker)WNPSH in WRF4_LICOM(RegCM4_LICOM)was driven by overestimated(underestimated)diabatic heating,which peaked at approximately 450 hPa over the region around the Philippines in association with different condensation–radiation processes.Coupling of WRF4 with LIOCM is a crucial step towards the development of the next generation of regional earth system models at the Chinese Academy of Sciences.
基金supported by the National Natural Science Foundation of China(Grant No.41375097)the Jiangsu Collaborative Innovation Center for Climate Change
文摘The time-mean and interannual variability of the interface between the Indian summer monsoon and East Asian summer monsoon （IIE） was assessed using both Max-Planck-Institute Earth System Model （MPI-ESM） and ECHAM5/MPI-OM and by calculating diagnostics and skill metrics around the IIE area. Progress has been made in modeling these aspects by moving from ECHAM5/MPI-OM to MPI-ESM. MPI-ESM is more skillful than ECHAM5/MPI-OM in modeling the time-mean state and the extreme condition of the IIE. Though simulation of the interannual variability significantly deviates to some extent in both MPI-ESM and ECHAM5/MPI-OM, MPI-ESM-LR shows better skill in reflecting the relationship among sea surface temperature anomalies over the Pacific, circulation anomalies over East Asia, and liE variability. The temperature becomes warmer under the RCP2.6 and RCP8.5 scenarios in comparison with the historical experiments, but the position of the liE and the key physical process in relation to the IIE variability almost remains the same, suggesting that the Indian summer monsoon tends to change in phase with the East Asian summer monsoon under each RCP scenario. The relatively realistic description of the physical processes modulated by terrain in MPI-ESM may be one of the most important reasons why MPI-ESM performs better in simulating the liE.
基金supported by the National Key Basic Research and Development Plan (No.2015CB953900)the Natural Science Foundation of China (Nos.41330960 and 41776032)
文摘Version 4(v4) of the Extended Reconstructed Sea Surface Temperature(ERSST) dataset is compared with its precedent, the widely used version 3b(v3b). The essential upgrades applied to v4 lead to remarkable differences in the characteristics of the sea surface temperature(SST) anomaly(SSTa) in both the temporal and spatial domains. First, the largest discrepancy of the global mean SSTa values around the 1940 s is due to ship-observation corrections made to reconcile observations from buckets and engine intake thermometers. Second, differences in global and regional mean SSTa values between v4 and v3b exhibit a downward trend(around-0.032℃ per decade) before the 1940s, an upward trend(around 0.014℃ per decade) during the period of 1950–2015, interdecadal oscillation with one peak around the 1980s, and two troughs during the 1960s and 2000s, respectively. This does not derive from treatments of the polar or the other data-void regions, since the difference of the SSTa does not share the common features. Third, the spatial pattern of the ENSO-related variability of v4 exhibits a wider but weaker cold tongue in the tropical region of the Pacific Ocean compared with that of v3b, which could be attributed to differences in gap-filling assumptions since the latter features satellite observations whereas the former features in situ ones. This intercomparison confirms that the structural uncertainty arising from underlying assumptions on the treatment of diverse SST observations even in the same SST product family is the main source of significant SST differences in the temporal domain. Why this uncertainty introduces artificial decadal oscillations remains unknown.
基金funded by the Cultivating Project of Strategic Priority Research Program of Chinese Academy of Science(No.XDPB1903)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA19040202)+1 种基金the National Nature Science Foundation of China(Nos.91744203,41571130034,and 92044302)the China National Key R&D Program(No.2018YFC0213205)
文摘Spatiotemporal variations of ozone(O_(3))taken from the Copernicus Atmosphere Monitoring Service(CAMS)and the second Modern-Era Retrospective Analysis for Research and Applications(MERRA-2)were intercompared and evaluated with ground and ozone-sonde observations over China in 2018 and 2019.Intercomparison of the surface ozone from CAMS and MERRA-2 reanalysis showed significant negative bias(CAMS minus MERRA-2,same below)at Tibetan Plateau of up to 80μg/m^(3),and the average R^(2)was about 0.6 across China.Evaluated with the ground observations from China National Environmental Monitoring Center(CNEMC),we found that CAMS and MERRA-2 reanalysis were capable of capturing the key patterns of monthly and diurnal variations of surface ozone over China except for the western region,and MERRA-2 overestimated the observations compared to CAMS.Vertically,the CAMS profiles overestimated the ozone-sonde from the World Ozone and Ultraviolet Radiation Data Center(WOUDC)above 200 h Pa with the magnitude reaching up to 150μg/m3,while little bias was found between the reanalysis and observations below 200 h Pa.Intercomparison drawn from the vertical distribution between CAMS and MERRA-2 reanalysis showed that the negative bias appeared throughout the troposphere over China,while the positive bias emerged in the upper troposphere and lower stratosphere(UTLS)with high order of magnitude exceeding 100μg/m^(3),indicating large uncertainties at higher altitudes.In summary,we concluded that CAMS reanalysis showed better agreement with the observations in contrast to MERRA-2,and the large discrepancy especially at higher altitudes between these two reanalysis datasets could not be ignored.
文摘A model intercomparison in terms of surface air temperature annual cycle amplitude-phase characteristics (SAT AC APC) is performed. The models included in the intercomparison belong to two groups: five atmospheric models with prescribed sea surface temperature and sea ice cover and four coupled models forced by the atmospheric abundances of anthropogenic constituents (in total six coupled model simulations). Over land, the models, simulating higher than observed time averaged SAT, also tend to simulate smaller than observed amplitude of its annual and semiannual harmonics and (outside the Tropics) later-than-observed spring and autumn moments. The models with larger (smaller) time averaged amplitudes of annual and semiannual harmonics also tend to simulate larger (smaller) interannual standard deviations. Over the oceans, the coupled models with larger interannual standard deviations of annual mean SAT tend to simulate larger interannual standard deviations of both annual and semiannual SAT harmonics amplitudes. Most model errors are located in the belts 60°–70°N and 60°–70°S and over Antarctica. These errors are larger for those coupled models which do not employ dynamical modules for sea ice. No systematic differences are found in the simulated time averaged fields of the surface air temperature annual cycle characteristics for atmospheric models on one hand and for the coupled models on the other. But the coupled models generally simulate interannual variability of SAT AC APC better than the atmospheric models (which tend to underestimate it). For the coupled models, the results are not very sensitive to the choice of the particular scenario of anthropogenic forcing. There is a strong linear positive relationship between the model simulated time averaged semiannual SAT harmonics amplitude and interannual standard deviation of annual mean SAT. It is stronger over the tropical oceans and is weaker in the extratropics. In the tropical oceanic areas, it is stronger for the coupled than for the atmospheric models.
基金jointly supported by the National Key Research and Development Program of China [grant number2016YFE0201400]the Basic Research Program of the State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry,Institute of Atmospheric Physics,Chinese Academy of Sciences [grant number 7-082999]
文摘This analysis of the multi-model aerosol optical depth (AOD) in eastern China using the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) datasets shows that the global models underestimate the AOD by 33% and 44% in southern and northern China, respectively, and decrease the relative humidity (RH) of the air in the surface layer to 71%–80%, which is less than the RH of 77%–92% in reanalysis meteorological datasets. This indicates that the low biases in the RH partially account for the errors in the AOD. The AOD is recalculated based on the model aerosol concentrations and the reanalysis humidity data. Improving the mean value of the RH increases the multi-model annual mean AOD by 45% in southern China and by 33% in June–August in northern China. This method of improving the AOD is successful in most of the ACCMIP models, but it is unlikely to be successful in GISS-E2-R, in which the plot of its AOD efficiency against RH strongly deviates from the rest of the models. The effect of the improvement in the modeled RH on the AOD depends on the concentration of aerosols. The shape error in the frequency distribution of the RH is likely to be more important than the error in the mean value of the RH, but this requires further research.
基金Under the auspices of the Yunnan Scientist Workstation on International River Research of Daming He(No.KXJGZS-2019-005)National Natural Science Foundation of China(No.42201040)+1 种基金National Key Research and Development Project of China(No.2016YFA0601601)China Postdoctoral Science Foundation(No.2023M733006)。
文摘Within the context of the Belt and Road Initiative(BRI)and the China-Myanmar Economic Corridor(CMEC),the Dulong-Ir-rawaddy(Ayeyarwady)River,an international river among China,India and Myanmar,plays a significant role as both a valuable hydro-power resource and an essential ecological passageway.However,the water resources and security exhibit a high degree of vulnerabil-ity to climate change impacts.This research evaluates climate impacts on the hydrology of the Dulong-Irrawaddy River Basin(DIRB)by using a physical-based hydrologic model.We crafted future climate scenarios using the three latest global climate models(GCMs)from Coupled Model Intercomparison Project 6(CMIP6)under two shared socioeconomic pathways(SSP2-4.5 and SSP5-8.5)for the near(2025-2049),mid(2050-2074),and far future(2075-2099).The regional model using MIKE SHE based on historical hydrologic processes was developed to further project future streamflow,demonstrating reliable performance in streamflow simulations with a val-idation Nash-Sutcliffe Efficiency(NSE)of 0.72.Results showed that climate change projections showed increases in the annual precip-itation and potential evapotranspiration(PET),with precipitation increasing by 11.3%and 26.1%,and PET increasing by 3.2%and 4.9%,respectively,by the end of the century under SSP2-4.5 and SSP5-8.5.These changes are projected to result in increased annual streamflow at all stations,notably at the basin’s outlet(Pyay station)compared to the baseline period(with an increase of 16.1%and 37.0%at the end of the 21st century under SSP2-4.5 and SSP5-8.5,respectively).Seasonal analysis for Pyay station forecasts an in-crease in dry-season streamflow by 31.3%-48.9%and 22.5%-76.3%under SSP2-4.5 and SSP5-8.5,respectively,and an increase in wet-season streamflow by 5.8%-12.6%and 2.8%-33.3%,respectively.Moreover,the magnitude and frequency of flood events are pre-dicted to escalate,potentially impacting hydropower production and food security significantly.This research outlines the hydrological response to future climate change during the 21st century and offers a scientific basis for the water resource management strategies by decision-makers.
基金supported by the Laoshan Laboratory[grant number LSKJ202202403]the National Natural Science Foundation of China[grant number 42030410]+1 种基金additionally supported by the Startup Foundation for Introducing Talent of NUISTJiangsu Innovation Research Group[grant number JSSCTD202346]。
文摘Global warming induced by increased CO_(2) has caused marked changes in the ocean.Previous estimates of ocean salinity change in response to global warming have considerable ambiguity,largely attributable to the diverse sensitivities of surface fluxes.This study utilizes data from the Flux-Anomaly-Forced Model Intercomparison Project to investigate how ocean salinity responds to perturbations of surface fluxes.The findings indicate the emergence of a sea surface salinity(SSS)dipole pattern predominantly in the North Atlantic and Pacific fresh pools,driven by surface flux perturbations.This results in an intensification of the“salty gets saltier and fresh gets fresher”SSS pattern across the global ocean.The spatial pattern amplification(PA)of SSS under global warming is estimated to be approximately 11.5%,with surface water flux perturbations being the most significant contributor to salinity PA,accounting for 8.1% of the change after 70 years in experiments since pre-industrial control(piControl).Notably,the zonal-depth distribution of salinity in the upper ocean exhibits lighter seawater above the denser water,with bowed isopycnals in the upper 400 m.This stable stratification inhibits vertical mixing of salinity and temperature.In response to the flux perturbations,there is a strong positive feedback due to consequent freshening.It is hypothesized that under global warming,an SSS amplification of 7.2%/℃ and a mixed-layer depth amplification of 12.5%/℃ will occur in the global ocean.It suggests that the salinity effect can exert a more stable ocean to hinder the downward transfer of heat,which provides positive feedback to future global warming.
基金Supported by the National Natural Science Foundation of China(41125017 and 41330423)LASG/IAP Funding for the Development of Climate System Model
文摘The development of coupled earth/climate system models in China over the past 20 years is reviewed, including a comparison with other international models that participated in the Coupled Model Intercom- parison Project （CMIP） from phase 1 （CMIP1） to phase 4 （CMIP4）. The Chinese contribution to CMIP is summarized, and the major achievements from CMIP1 to CMIP3 are listed as a reference for assessing the strengths and weaknesses of Chinese models. After a description of CMIP5 experiments, the five Chinese models that participated in CMIP5 are then introduced. Furthermore, following a review of the current status of international model development, both the challenges and opportunities for the Chinese climate modeling community are discussed. The development of high-resolution climate models, earth system mod- els, and improvements in atmospheric and oceanic general circulation models, which are core components of earth/climate system models, are highlighted. To guarantee the sustainable development of climate system models in China, the need for national-level coordination is discussed, along with a list of the main compo- nents and supporting elements identified by the US National Strategy for Advancing Climate Modeling.
文摘The AHI-FSA(Advanced Himawari Imager-Fire Surveillance Algorithm)is a recently developed algorithm designed to support wildfire surveillance and mapping using the geostationary Himawari-8 satellite.At present,the AHI-FSA algorithm has only been tested on a number of case study fires in Western Australia.Initial results demonstrate potential as a wildfire surveillance algorithm providing high frequency(every 10 minutes),multi-resolution fire-line detections.This paper intercompares AHI-FSA across the Northern Territory of Australia(1.4 million km2)over a ten-day period with the well-established fire products from LEO(Low Earth Orbiting)satellites:MODIS(Moderate Resolution Imaging Spectroradiometer)and VIIRS(Visible Infrared Imaging Radiometer Suite).This paper also discusses the difficulties and solutions when comparing high temporal frequency fire products with existing low temporal resolution LEO satellite products.The results indicate that the multi-resolution approach developed for AHI-FSA is successful in mapping fire activity at 500 m.When compared to the MODIS,daily AHIFSA omission error was only 7%.High temporal frequency data also results in AHI-FSA observing fires,at times,three hours before the MODIS overpass with much-enhanced detail on fire movement.
基金This work was supported by NOAA PSDI program(NA11NES4400012),and Chinese Academy of Sciences/State Administration of Foreign Experts Affairs(CAS/SAFEA)International Partnership Program(KZZD-EW-TZ-09).
文摘In recent years,algorithms have been developed to derive land surface temperature(LST)from geostationary and polar satellite systems.However,few works have addressed the intercomparison between Geostationary Operational Environmental Satellites(GOES)and the available suite of polar sensors.In this study,differences in LSTs between GOES and MODerate resolution Imaging Spectroradiometer(MODIS)have been compared and also evaluated against ground observations.Due to the lack of split-window(SW)channels in the GOES M(12)-Q era,a dual-window algorithm using a mid-infrared 3.9µm channel is compared with traditional SW algorithm.It is found that the differences in LST between different platforms are bigger during daytime than those during nighttime.During daytime,LSTs from GOES with the dualwindow algorithm are warmer than MODIS LSTs,while LSTs from the SW algorithm are close to MODIS LSTs.The difference during daytime is found to be related to anisotropy in satellite viewing geometry,and land surface properties,such as vegetation cover and especially surface emissivity at middle infrared(MIR)channel.When evaluated against ground observations,the standard deviation(precision)error(2.35 K)from the dual window algorithm is worse than that(1.83 K)from the SW algorithm,indicating the lack of split-window channel in the GOES M(12)-Q era may degrade the performance of LST retrievals.
基金This work was supported in part by NASA Grant#NNX14AI68G.
文摘We characterize the agreement and disagreement of four publically available burned products(Fire CCI,Copernicus Burnt Area,MODIS MCD45A1,and MODIS MCD64A1)at a finer spatial and temporal scale than previous assessments using a grid of three-dimensional cells defined both in space and in time.Our analysis,conducted using seven years of data(2005–2011),shows that estimates of burned area vary greatly between products in terms of total area burned,the location of burning,and the timing of the burning.We use regional and monthly units for analysis to provide insight into the variation between products that can be lost when considering products yearly and/or globally.Comparison with independent,contemporaneous MODIS active fire observations provides one indication of which products most reasonably capture the burning regime.Our results have implications for the use of global burned area products in fire ecology,management and emissions applications.
基金jointly supported by the NSFC project (42088101, 41975048, 42361144843, 42175069)。
文摘This paper evaluates a representation of winter stratospheric circulation in the Antarctic that is based on CRA-40, a 40-year global reanalysis dataset released by the China Meteorological Administration, and compares it with representations based on two other state-of-the-art reanalysis datasets: the fifth-generation atmospheric reanalysis provided by the European Centre for Medium-Range Weather Forecasts(ERA-5) and the Modern-Era Retrospective analysis for Research and Applications, version 2(MERRA-2). In terms of climatology, we find that CRA-40 portrays a stronger and colder polar vortex in the middle and lower stratosphere than ERA-5, but a weaker and warmer one than MERRA-2. However, disagreement among the three reanalyses is confined mainly to the period before1999, and is largely reduced after that time. On the interannual timescale, portrayals of the intensity and area of the 10-hPa polar vortex are quite consistent among the three reanalyses, with correlation coefficients greater than 0.9 between each pair of reanalyses. In addition, the central dates of most sudden stratospheric deceleration(SSD) events at 10 hPa in the three reanalyses differ by less than one day, indicating that CRA-40 is also highly consistent with the other two reanalysis datasets regarding daily evolution. Our analyses suggest that CRA-40 performs comparably to ERA-5 and MERRA-2 in characterizing winter circulation in the Antarctic middle and lower stratosphere.
基金supported by the National Natural Science Foundation of China(Grant Nos.42375062 and 42275158)the National Key Scientific and Technological Infrastructure project“Earth System Science Numerical Simulator Facility”(EarthLab)the Natural Science Foundation of Gansu Province(Grant No.22JR5RF1080)。
文摘It is fundamental and useful to investigate how deep learning forecasting models(DLMs)perform compared to operational oceanography forecast systems(OFSs).However,few studies have intercompared their performances using an identical reference.In this study,three physically reasonable DLMs are implemented for the forecasting of the sea surface temperature(SST),sea level anomaly(SLA),and sea surface velocity in the South China Sea.The DLMs are validated against both the testing dataset and the“OceanPredict”Class 4 dataset.Results show that the DLMs'RMSEs against the latter increase by 44%,245%,302%,and 109%for SST,SLA,current speed,and direction,respectively,compared to those against the former.Therefore,different references have significant influences on the validation,and it is necessary to use an identical and independent reference to intercompare the DLMs and OFSs.Against the Class 4 dataset,the DLMs present significantly better performance for SLA than the OFSs,and slightly better performances for other variables.The error patterns of the DLMs and OFSs show a high degree of similarity,which is reasonable from the viewpoint of predictability,facilitating further applications of the DLMs.For extreme events,the DLMs and OFSs both present large but similar forecast errors for SLA and current speed,while the DLMs are likely to give larger errors for SST and current direction.This study provides an evaluation of the forecast skills of commonly used DLMs and provides an example to objectively intercompare different DLMs.
