Journal Article•
Preliminary Comparison and Analysis between ERA-40,NCEP-2 Reanalysis and Observations over China
TL;DR: In this paper, a preliminary intercomparison of monthly mean surface 2 m temperature and precipitation is made between the ERA-40, NCEP-2 reanalysis and the observations to validate the reliability of the reanalysis over China.
Abstract: The Reanalysis datasets are widely used in climate change research,but the reliability of the reanalysis datasets at different time-spatial scale can also impact the results of the study.An preliminary intercomparison of monthly mean surface 2 m temperature and precipitation are made between the ERA-40,NCEP-2 reanalysis and the observations to validate the reliability of the reanalysis over China.The results show that the temporal and spatial distribution of temperature and precipitation for the ERA-40 and NCEP-2 are similar with the observed counterparts,although some differences can be aware of in the west region of China,especially in Tibet Platean.In terms of reliability,the temperature is higher than the precipitation,the East than the West,and the ERA-40 than the NCEP-2.
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TL;DR: In this article, the authors examined the relationship between elevation and temperature trend magnitudes on an annual or seasonal basis in the surface data or ERA-40, and in NCEP this relationship is inconsistent.
219 citations
TL;DR: In this article, the correspondence between precipitation products from atmospheric reanalyses (ERA-40, NCEP-1, and N CEP-2), the Climate Prediction Center (CPC) Merged Analyses of Precipitation (CMAP-1 and CMAP-2, and the Global PrecIPitation Climatology Project Version 2 (GPCP--2) with adjusted observational precipitation (AOP) from China for 1979-2001 and also for ERA-40 and NCEPs-1 over 1958-1978.
Abstract: [1] We assess the correspondence between precipitation products from atmospheric reanalyses (ERA-40, NCEP-1, and NCEP-2), the Climate Prediction Center (CPC) Merged Analyses of Precipitation (CMAP-1 and CMAP-2), and the Global Precipitation Climatology Project Version 2 (GPCP-2) with adjusted observational precipitation (AOP) from China for 1979–2001 and also for ERA-40 and NCEP-1 over 1958–1978. In general, we conclude that CMAP-1 and GPCP-2 agree more closely with AOP than the reanalysis products do, although ERA-40 data agree more closely with AOP than NCEP data. The percentages of precipitation differences (PPDs) across China between annual ERA-40, NCEP-1, NCEP-2, CMAP-1, CMAP-2, and GPCP-2 data and AOP are −12, 22, 14, −8, −7, and −15%, respectively, for 1979–2001. Although relatively small biases are evident for China as a whole, maximum PPDs, usually occurring around the Qinghai-Tibetan Plateau, can exceed 1000%, indicating a strong terrain dependence of gridded precipitation data. GPCP-2, although characterized by greater underestimation for most of China compared with CMAP-1, exhibits a smaller biases range and hence may be better than CMAP-1. Compared with the NCEP-1 system, NCEP-2 represents an improvement as NCEP-2 precipitation agrees more closely with AOP than NCEP-1 data. However, the coherence of NCEP-2 precipitation needs further improvement. In addition, we find worse consistency and accuracy and larger positive biases in some parts of China for CMAP-2 versus CMAP-1, illustrating an advantage of including reanalysis data in CMAP, as CMAP-1 does. CMAP-1 could be further improved if they used the more skillful ERA-40 precipitation instead of the NCEP/NCAR data.
144 citations
TL;DR: In this paper, the authors compare temperatures and their trends from 71 homogenized surface stations (with elevations above 2000 m a.s.l.) with National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis and European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-40 hereafter) in the eastern and central TP during 1961-2004.
Abstract: The Tibetan Plateau (TP) with an average elevation of over 4000 m a.s.l. is the world's highest and most extensive highland. The scarcity of climatic observations limits our understanding of surface air temperature change in the region. Thus, we compare temperatures and their trends from 71 homogenized surface stations (with elevations above 2000 m a.s.l.) with National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis (NCEP/NCAR hereafter) and European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-40 hereafter) in the eastern and central TP during 1961–2004. For current climatology, ERA-40 is more similar to the surface stations than NCEP/NCAR. Compared with surface stations, both NCEP/NCAR and ERA-40 reanalyses have cold biases, which are mainly a result of differences in topographical height, and station aspect and slope. Warming trends at the surface stations are on average stronger than in both reanalyses, but ERA-40 captures the surface warming more clearly than NCEP/NCAR on an annual and seasonal basis. Since ERA-40 more closely represents the surface temperatures and their trends in the central and eastern TP, ERA-40 predictions are selected to examine change in the western TP where there are few surface stations. NCEP/NCAR, on the other hand, is more representative of free air temperature conditions. The ‘observation minus reanalysis’ (OMR) method can be used to estimate the impact of surface changes on climate by computing the difference between surface observations and NCEP/NCAR (which only contains the forcing influencing the assimilated atmospheric trends). The OMR trend is significantly increasing but the extent to which the changes in local environment are responsible needs further study. Copyright © 2012 Royal Meteorological Society
136 citations
Cites background or result from "Preliminary Comparison and Analysis..."
...This finding is consistent with other studies (Frauenfeld et al., 2005; Zhao and Fu, 2006; Ma et al., 2008; Zhao et al., 2008)....
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...The complex elevated topography of the TP means that the differences in elevation between surface stations and the ERA-40 and NCEP/NCAR reanalyses model elevations are not trivial (Zhao and Fu, 2006; Ma et al., 2008)....
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TL;DR: In this paper, the correspondence of reanalysis air temperatures from ERA-40, NCEP-1, and N CEP-2 with homogenized observational data from China for 1958-2001 and 1979-2001 was assessed.
Abstract: [1] We assess the correspondence of reanalysis air temperatures from ERA-40, NCEP-1, and NCEP-2 with homogenized observational data from China for 1958–2001 and 1979–2001. Results indicate that climatologies for annual ERA-40, NCEP-1, and NCEP-2 air temperatures are lower than observations by −0.93°C, −2.78°C, and −2.27°C, respectively. Large negative differences for most of western China primarily contribute to this cool bias. Error analysis indicates that the internal coherence of ERA-40 data is better than NCEP-1 or NCEP-2. Although NCEP-2 air temperatures represent an improvement over NCEP-1, biases of NCEP-1 and NCEP-2 data relative to observations are still much larger than for ERA-40. Areas with positive/negative air temperature differences (dT) between reanalysis and observational data correspond to negative/positive elevation differences (dH). The high correlation coefficients of −0.94, −0.88, and −0.85 between dT and dH for ERA-40, NCEP-1, NCEP-2, and observations, respectively, illustrate that the air temperature differences between reanalysis data and observations are primarily related to elevation differences. Furthermore, a spatial and temporal comparison of trends also indicates that ERA-40 temperature changes correspond most closely to observed trends in China. In general, our comprehensive analysis of the three global reanalysis products indicates that, both on a seasonal and annual basis, ERA-40 temperatures correspond most closely to observations, and biases are due mainly to the elevation differences.
119 citations
TL;DR: In this article, the verifications of ERA-Interim precipitation and temperature in mainland China were conducted using a global and regional scale model, which is a valid proxy for observations at local and regional scales.
Abstract: ERA-Interim has been widely considered as a valid proxy for observations at global and regional scales. However, the verifications of ERA-Interim precipitation and temperature in mainland C...
84 citations