Contrasting Daytime and Nighttime Precipitation Variability between Observations and Eight Reanalysis Products from 1979 to 2014 in China

Daytime (0800–2000 Beijing time) and nighttime (2000–0800 Beijing time) precipitation at approximately 2100 stations in China from 1979 to 2014 was used to evaluate eight current reanalyses. Daytime, nighttime, and nighttime–daytime contrast of precipitation were examined in aspects of climatology, seasonal cycle, interannual variability, and trends. The results show that the ECMWF interim reanalysis (ERA-Interim), ERA-Interim/Land, Japanese 55-year Reanalysis (JRA-55), and NCEP Climate Forecast System Reanalysis (CFSR) can reproduce the observed spatial pattern of nighttime–daytime contrast in precipitation amount, exhibiting a positive center over the eastern Tibetan Plateau and a negative center over southeastern China. All of the reanalyses roughly reproduce seasonal variations of nighttime and daytime precipitation, but not always nighttime–daytime contrast. The reanalyses overestimate drizzle and light precipitation frequencies by greater than 31.5% and underestimate heavy precipitation frequencies by less than −30.8%. The reanalyses successfully reproduce interannual synchronizations of daytime and nighttime precipitation frequencies and amounts with an averaged correlation coefficient r of 0.66 against the observed data but overestimate their year-to-year amplitudes by approximately 64%. The trends in nighttime, daytime, and nighttime–daytime contrast of the observed precipitation amounts are mainly dominated by their frequencies ( r = 0.85). Less than moderate precipitation frequency has exhibited a significant downward trend (−2.5% decade−1 during nighttime and −1.7% decade−1 during daytime) since 1979, which is roughly captured by the reanalyses. However, only JRA-55 captures the observed trend of nighttime precipitation intensity (2.4% decade−1), while the remaining reanalyses show negative trends. Overall, JRA-55 and CFSR provide the best reproductions of the observed nighttime–daytime contrast in precipitation intensity, although they have considerable room for improvement.

Dominant Modes of Wintertime Upper-Tropospheric Temperature Variations over Asia and Links to Surface Climate

In this study, the authors investigate the variations and predictability of wintertime upper-tropospheric temperature (UTT) over Asia, which are often linked to severe climate anomalies, and the associated features of large-scale circulation and surface climate. The ECMWF Interim Re-Analysis (ERA-Interim) and hindcast of the NCEP Climate Forecast System, version 2 (CFSv2), are mainly analyzed. The first empirical orthogonal function mode of UTT shows a dipole structure, with a strong positive center over southern China and a weak negative center over Mongolia. The second mode is featured by a monopole variation, with a positive center appearing from the northwestern Tibetan Plateau (TP) to Japan. The third mode exhibits a tripole pattern, with two positive centers over Pakistan and the Sea of Japan and a negative center over central Asia. The first mode is linked to El Niño–Southern Oscillation, accompanied by surface warming over the southeastern TP and deficient precipitation over southern China, the Korean Peninsula, and from equatorial East Africa to the east of the TP. The second mode is associated with circulation anomalies similar to those associated with the Arctic Oscillation, with significant warming over East Asia. The third mode features two wave trains and is linked to the Middle East jet stream, and is associated with excessive precipitation from the eastern TP to southern Japan. The CFSv2 can predict the first mode skillfully by several months in advance, but it shows little skill in predicting the second and third modes.