The first Chinese microwave ocean environment satellite HY-2A was launched successfully in August,2011. This study presents a quality assessment of HY-2A scatterometer(HYSCAT) data based on comparison with ocean buoy ...The first Chinese microwave ocean environment satellite HY-2A was launched successfully in August,2011. This study presents a quality assessment of HY-2A scatterometer(HYSCAT) data based on comparison with ocean buoy data,the Advanced Scatterometer(ASCAT) data,and numerical model data from the National Centers for Environmental Prediction(NCEP). The in-situ observations include those from buoy arrays operated by the National Data Buoy Center(NDBC) and Tropical Atmosphere Ocean(TAO) project. Only buoys located offshore and in deep water were analyzed. The temporal and spatial collocation windows between HYSCAT data and buoy observations were 30 min and 25 km,respectively. The comparisons showed that the wind speeds and directions observed by HYSCAT agree well with the buoy data. The root-mean-squared errors(RMSEs) of wind speed and direction for the HYSCAT standard wind products are 1.90 m/s and 22.80°,respectively. For the HYSCAT-ASCAT comparison,the temporal and spatial differences were limited to 1 h and 25 km,respectively. This comparison yielded RMSEs of 1.68 m/s for wind speed and 19.1° for wind direction. We also compared HYSCAT winds with reanalysis data from NCEP. The results show that the RMSEs of wind speed and direction are 2.6 m/s and 26°,respectively. The global distribution of wind speed residuals(HYSCAT-NCEP) is also presented here for evaluation of the HYSCAT-retrieved wind field globally. Considering the large temporal and spatial differences of the collocated data,it is concluded that the HYSCAT-retrieved wind speed and direction met the mission requirements,which were 2 m/s and 20° for wind speeds in the range 2–24 m/s. These encouraging assessment results show that the wind data obtained from HYSCAT will be useful for the scientific community.展开更多
The South Asian Highs (SAHs) at 100 hPa over China in the three reanalysis datasets NCEP1, NCEP2, and ERA-40 are evaluated by using station observation data. The results demonstrate a substantial discrepancy even betw...The South Asian Highs (SAHs) at 100 hPa over China in the three reanalysis datasets NCEP1, NCEP2, and ERA-40 are evaluated by using station observation data. The results demonstrate a substantial discrepancy even between the reanalyses. First, the data of the three reanalyses generally underestimate the intensity of the SAH in the China domain. Second, there are interdecadal changes in the SAH, with highs in the 1960s and 1980s and lows in the 1970s, 1990s, and 2000s. This interdecadal variation of the SAH can be well depicted with NCEP1 data, but the high in the 1980s is missed by ERA-40. The NCEP2 corresponds well with NCEP 1 and captures the decreasing trend after 1979. Furthermore, the NCEP1 reanalysis overestimates the interdecadal changes of SAH, while ERA-40 underestimates the interdecadal changes. This work suggests that much caution should be exerted when the reanalysis datasets are adopted to study the interdecadal variability of SAH.展开更多
The trend in the atmospheric heat source over the central and eastern Tibetan Plateau (CE-TP) is quantitatively estimated using historical observations at 71 meteorological stations, three reanalysis datasets from 198...The trend in the atmospheric heat source over the central and eastern Tibetan Plateau (CE-TP) is quantitatively estimated using historical observations at 71 meteorological stations, three reanalysis datasets from 1980-2008, and two satellite radiation datasets from 1984-2007. Results show that a weakening of sensible heat (SH) flux over the CE-TP continues. The most significant trend occurs in spring, induced mainly by decelerated surface wind speeds. The ground-air temperature difference shows a notable increasing trend over the last 5 years. Trends in net radiation flux of the atmospheric column over the CE-TP, evaluated by two satellite radiation datasets, are clearly different. Trends in the atmospheric heat source calculated by the three reanalysis datasets are not completely consistent, and even show opposite signals. Results from the two datasets both show a weakening of the heat source but the magnitude of one is significantly stronger, whereas an increase is indicated by the other data. Therefore, it is challenging to accurately calculate the trend in the atmospheric heat source over the CE-TP, particularly from the estimates of the reanalysis datasets.展开更多
基金supported by the National Natural Science Foundation of China[grant number 41475078]Strategic Priority Research Program–Climate Change:Carbon Budget and Relevant Issues of the Chinese Academy of Sciences[grant number XDA05090105]
基金Supported by the National High Technology Research and Development Program of China(863 Program)(No.2013AA09A505)the National Natural Science Foundation of China(No.40906091)the Open Project of School of Marine Sciences,Nanjing University of Information Science and Technology(No.KHYS1304)
文摘The first Chinese microwave ocean environment satellite HY-2A was launched successfully in August,2011. This study presents a quality assessment of HY-2A scatterometer(HYSCAT) data based on comparison with ocean buoy data,the Advanced Scatterometer(ASCAT) data,and numerical model data from the National Centers for Environmental Prediction(NCEP). The in-situ observations include those from buoy arrays operated by the National Data Buoy Center(NDBC) and Tropical Atmosphere Ocean(TAO) project. Only buoys located offshore and in deep water were analyzed. The temporal and spatial collocation windows between HYSCAT data and buoy observations were 30 min and 25 km,respectively. The comparisons showed that the wind speeds and directions observed by HYSCAT agree well with the buoy data. The root-mean-squared errors(RMSEs) of wind speed and direction for the HYSCAT standard wind products are 1.90 m/s and 22.80°,respectively. For the HYSCAT-ASCAT comparison,the temporal and spatial differences were limited to 1 h and 25 km,respectively. This comparison yielded RMSEs of 1.68 m/s for wind speed and 19.1° for wind direction. We also compared HYSCAT winds with reanalysis data from NCEP. The results show that the RMSEs of wind speed and direction are 2.6 m/s and 26°,respectively. The global distribution of wind speed residuals(HYSCAT-NCEP) is also presented here for evaluation of the HYSCAT-retrieved wind field globally. Considering the large temporal and spatial differences of the collocated data,it is concluded that the HYSCAT-retrieved wind speed and direction met the mission requirements,which were 2 m/s and 20° for wind speeds in the range 2–24 m/s. These encouraging assessment results show that the wind data obtained from HYSCAT will be useful for the scientific community.
基金supported by the National Natural Science Foundation of China (Grant No. 40775053)the Ministry of Finance/Ministry of Science and Technology special funds for scientific research on public causes (Grant No GYHY200906018)
文摘The South Asian Highs (SAHs) at 100 hPa over China in the three reanalysis datasets NCEP1, NCEP2, and ERA-40 are evaluated by using station observation data. The results demonstrate a substantial discrepancy even between the reanalyses. First, the data of the three reanalyses generally underestimate the intensity of the SAH in the China domain. Second, there are interdecadal changes in the SAH, with highs in the 1960s and 1980s and lows in the 1970s, 1990s, and 2000s. This interdecadal variation of the SAH can be well depicted with NCEP1 data, but the high in the 1980s is missed by ERA-40. The NCEP2 corresponds well with NCEP 1 and captures the decreasing trend after 1979. Furthermore, the NCEP1 reanalysis overestimates the interdecadal changes of SAH, while ERA-40 underestimates the interdecadal changes. This work suggests that much caution should be exerted when the reanalysis datasets are adopted to study the interdecadal variability of SAH.
基金supported by the Chinese Ministry of Science and Technology (2010CB951703 and 2009CB421403)the Knowledge Innovation Program of Chinese Academy of Sciences (KZCX2-YW-Q11- 01)the National Natural Science Foundation of China (40975047)
文摘The trend in the atmospheric heat source over the central and eastern Tibetan Plateau (CE-TP) is quantitatively estimated using historical observations at 71 meteorological stations, three reanalysis datasets from 1980-2008, and two satellite radiation datasets from 1984-2007. Results show that a weakening of sensible heat (SH) flux over the CE-TP continues. The most significant trend occurs in spring, induced mainly by decelerated surface wind speeds. The ground-air temperature difference shows a notable increasing trend over the last 5 years. Trends in net radiation flux of the atmospheric column over the CE-TP, evaluated by two satellite radiation datasets, are clearly different. Trends in the atmospheric heat source calculated by the three reanalysis datasets are not completely consistent, and even show opposite signals. Results from the two datasets both show a weakening of the heat source but the magnitude of one is significantly stronger, whereas an increase is indicated by the other data. Therefore, it is challenging to accurately calculate the trend in the atmospheric heat source over the CE-TP, particularly from the estimates of the reanalysis datasets.
