Mesoscale simulations of gravity waves in the upper troposphere and lower stratosphere over North America and North Atlantic Ocean in January 2003 are compared with satellite radiance measurements from the Advanced Microwave Sounding Unit-A (AMSU-A). Four regions of strong gravity wave (GW) activities are found in the model simulations and the AMSU-A observations: the northwestern Atlantic, the U.S. Rockies, the Appalachians, and Greenland. GWs over the northwestern Atlantic Ocean are associated with the midlatitude baroclinic jet-front system, while the other three regions are apparently related to high topography. Model simulations are further used to analyze momentum fluxes in the zonal and meridional directions. It is found that strong westward momentum fluxes are prevalent over these regions over the whole period. Despite qualitative agreement between model simulations and satellite measurements, sensitivity experiments demonstrate that the simulated GWs are sensitive to the model spin-up time.

According to the Anderson-Darling principle, a method for forecast of extremely heavy rainfall (abbreviated as extreme rainfall/precipitation) was developed based on the ensemble forecast data of the T213 global ensemble prediction system (EPS) of the China Meteorological Administration (CMA). Using the T213 forecast precipitation data during 2007–2010 and the observed rainfall data in June–August of 2001–2010, characteristics of the cumulative distribution functions (CDFs) of the observed and the T213 EPS forecast precipitation were analyzed. Accordingly, in the light of the continuous differences of the CDFs between model climate and EPS forecasts, a mathematical model of Extreme Precipitation Forecast Index (EPFI) was established and applied to forecast experiments of several extreme rainfall events in China during 17–31 July 2011. The results show that the EPFI has taken advantage of the tail information of the model climatic CDF and provided agreeable forecasts of extreme rainfalls. The EPFI based on the T213 EPS is useful for issuing early warnings of extreme rainfalls 3–7 days in advance. With extension of the forecast lead time, the EPFI becomes less skillful. The results also demonstrate that the rationality of the model climate CDF was of vital importance to the skill of EPFI.

The long-term trends of total surface solar radiation (SSR), surface diffuse radiation, and surface air temperature were analyzed in this study based on updated 48-yr data from 55 observational stations in China, and then the correlation between SSR and the diurnal temperature range (DTR) was studied. The effect of total solar radiation on surface air temperature in China was investigated on the basis of the above analyses. A strong correlation between SSR and DTR was found for the period 1961–2008 in China. The highest correlation and steepest regression line slope occurred in winter, indicating that the solar radiation effect on DTR was the largest in this season. Clouds and water vapor have strong influences on both SSR and DTR, and hence on their relationship. The largest correlations between SSR and DTR occurred in wintertime in northern China, regardless of all-day (including clear days and cloudy days) or clear-day cases. Our results also showed that radiation arriving at the surface in China decreased significantly during 1961–1989 (dimming period), but began to increase during 1990–2008 (brightening period), in agreement with previous global studies. The reduction of total SSR offset partially the greenhouse warming during 1961–1989. However, with the increase of SSR after 1990, this offsetting effect vanished; on the contrary, it even made a contribution to the accelerated warming. Nonetheless, the greenhouse warming still played a controlling role because of the increasing of minimum and mean surface temperatures in the whole study period of 1961–2008. We estimated that the greenhouse gases alone may have caused surface temperatures to rise by 0.31–0.46°C (10 yr)−1 during 1961–2008, which is higher than previously estimated. Analysis of the corresponding changes in total solar radiation, diffuse radiation, and total cloud cover indicated that the dimming and brightening phenomena in China were likely attributable to increases in absorptive and scattering aerosols in the atmosphere, respectively.

Several numerical experiments were performed to investigate the dynamic and thermodynamic effects of sea surface temperature (SST) on tropical cyclone (TC) intensity. The results reveal that the relative SST within a radius of 2–3 times the radius of maximum wind contributes positively and greatly to TC intensity, while the remote SST far away from the TC center could reduce storm intensity. The change of air-sea temperature and moisture differences may be the reason why TC intensity is more sensitive to the relative rather than the absolute SST. As the inflow air moves toward the eyewall, warmer (colder) remote SST can gradually increase (decrease) the underlying surface air temperature and moisture, and thus decrease (increase) the air-sea temperature and moisture differences, which lead to less (more) energy fluxes entering the eyewall and then decrease (increase) the TC intensity and make it less sensitive to the absolute SST change. Finally, with all the related dynamic and thermodynamic processes being taken into account, a schematic diagram for the effects of relative SST and absolute SST on TC intensity is proposed.

A Tibetan ozone low was found in the 1990s after the Antarctic ozone hole. Whether this ozone low has been recovering from the beginning of the 2000s following the global ozone recovery is an intriguing topic. With the most recent merged TOMS/SBUV (Total Ozone Mapping Spectrometer/Solar Backscatter Ultra Violet) ozone data, the Tibetan ozone low and its long-term variation during 1979–2010 are analyzed using a statistical regression model that includes the seasonal cycle, solar cycle, quasi-biennial oscillation (QBO), ENSO signal, and trends. The results show that the Tibetan ozone low maintains and may become more severe on average during 1979–2010, compared with its mean state in the periods before 2000, possibly caused by the stronger downward trend of total ozone concentration over the Tibet. Compared with the ozone variation over the non-Tibetan region along the same latitudes, the Tibetan ozone has a larger downward trend during 1979–2010, with a maximum value of −0.40±0.10 DU yr−1 in January, which suggests the strengthening of the Tibetan ozone low in contrast to the recovery of global ozone. Regression analyses show that the QBO signal plays an important role in determining the total ozone variation over the Tibet. In addition, the long-term ozone variation over the Tibetan region is largely affected by the thermal-dynamical proxies such as the lower stratospheric temperature, with its contribution reaching around 10% of the total ozone change, which is greatly different from that over the non-Tibetan region.

In this paper, major features of the upper-tropospheric jet streams simulated by a coupled Climate System Model BCC_CSM1.1 are evaluated through comparison with the NCEP/NCAR reanalysis. The jet streams consist of the East Asian subtropical jet (EASJ) and the East Asian polar-front jet (EAPJ). Associated stationary wave and synoptic-scale transient eddy activities (STEA) are also examined. The results show that the climatological positions of the westerly jet streams are well captured by BCC_CSM1.1, but with slight intensity biases. Statistics from the 6-h model outputs reveal that the jet core number (JCN) of ESPJ is significantly underestimated. Examination of the simulated seasonal evolution of the westerly jet stream indicates that the model has produced a westward movement of the EASJ core in May, one month earlier than that in the reanalysis. Analysis of stationary wave activities shows that the overestimated meridional wind component may have caused considerable enhancement of meridional momentum and heat transport. The stationary Rossby wave represented by the wave activity flux at the southern flank of the Tibetan Plateau is favorable to the growth of asymmetric zonal wind and the multiple-center pattern of JCN. Unlike the stationary wave heat flux transport, the model tends to systematically generate weaker transient heat flux over East Asia. Further analysis of STEA exhibits a general consistent pattern between the simulation and the reanalysis, while the intensity of the northern STEA branch associated with the EAPJ is greatly reduced. The deficiencies of eddy momentum and heat flux transport and accompanied eddy forcing may contribute to the biases of the simulated upper-tropospheric jet streams, suggesting the potential importance of midlatitude internal atmospheric dynamics in shaping the tropospheric general circulation, which is not yet fully and accurately resolved in the current BCC_CSM1.1.

A method for using height reassignment to improve the quality of satellite-derived atmospheric motion vectors (AMVs) is presented. The rationale underlying height reassignment is explored, and the technical details are studied by applying three height reassignment schemes that use NCEP reanalysis winds. The quality of the AMVs is generally improved following reassignment, although the magnitude of the improvement differs according to the scheme applied. Scheme 3 provides the best quality and stability, followed by Scheme 1 and Scheme 2. The negative biases in the zonal components of the AMVs decrease from [−5, −4] m s−1 to <−1 m s−1 following reassignment. The meridional components also improve. The AMVs derived from the infrared and water vapor channels improve by 58.7% and 25%, respectively. The feasibility of using Scheme 3 in the operational derivation of AMVs is studied by incorporating the forecast wind field predicted by a T511 medium-range numerical weather prediction (NWP) system. Incorporating the 12-h forecast reduces the negative biases in zonal winds and positive biases in meridional winds retrieved from the water vapor channel, improving the overall quality of the AMVs by 26.7%. Extending the validity period of the forecast field linearly reduces the improvement in retrieved AMVs, but the magnitude of this reduction is small. Incorporating the 120-h forecast field still results in a 13% improvement, although it may eliminate a larger number of AMVs of good quality.

The sea surface temperature (SST) of the tropical western Pacific Ocean (TWPO) showed a pronounced warming in the late 1990s. Using numerical experiments of a regional climate model (RegCM), we analyzed the impact of this warming on rainfall over the Yangtze-Huaihe River valley of China during the Meiyu period (June–July). The model results revealed that the observed decadal changes in Meiyu rainfall since the late 1990s can be reproduced by a control experiment forced by the observed SST. Additionally, the sensitivity experiments suggested that the warming trend in the TWPO played a substantial role in the northward shift of the Meiyu belt in the late 1990s.

The spatial patterns of precipitation anomalies during five 30-yr warm periods of 691–720, 1231–1260, 1741–1770, 1921–1950, and 1981–2000 were investigated using a dryness/wetness grading dataset covering 48 stations from Chinese historical documents and 22 precipitation proxy series from natural archives. It was found that the North China Plain (approximately 35°–40°N, east of 105°E) was dry in four warm periods within the centennial warm epochs of 600–750, the Medieval Warm Period (about 900–1300) and after 1900. A wet condition prevailed over most of China during 1741–1770, a 30-yr warm peak that occurred during the Little Ice Age (about 1650–1850). The spatial pattern of the precipitation anomaly in 1981–2000 over East China (25°-40°N, east of 105°E) is roughly consistent with that in 1231–1260, but a difference in the precipitation anomaly appeared over the Tibetan Plateau. The spatial patterns of the precipitation anomalies over China varied between all five 30-yr warm periods, which implies that the matching pattern between temperature and precipitation change is multiform, and the precipitation anomaly could be positive or negative when a decadal warm climate occurs in different climate epochs. This result may provide a primary reference for the mechanism detection and climate simulation of the precipitation anomaly of the future warm climate.

A global ocean general circulation model, called LASG/IAP Climate system ocean model (LICOM), is employed to study the influence of climate change on the uptake and storage of anthropogenic CO2 in the global ocean. Two simulations were made: the control run (RUN1) with the climatological daily mean forcing data, and the climate change run (RUN2) with the interannually varying daily mean forcing data from the NCEP (National Centers for Environmental Prediction) of the US. The results show that the simulated distributions and storages of anthropogenic dissolved inorganic carbon (anDIC) from both runs are consistent with the data-based results. Compared with the data-based results, the simulations generate higher anDIC concentrations in the upper layer and lower storage amount of anDIC between the subsurface and 1000-m depth, especially in RUN1. A comparison of the two runs shows that the interannually varying forcing can enhance the transport of main water masses, so the rate of interior transport of anDIC is increased. The higher transfer rate of anDIC in RUN2 decreases its high concentration in the upper layer and increases its storage amount below the subsurface, which leads to closer distributions of anDIC in RUN2 to the data-based results than in RUN1. The higher transfer rate in RUN2 also induces larger exchange flux than in RUN1. It is estimated that the global oceanic anthropogenic CO2 uptake was 1.83 and 2.16 Pg C yr−1 in the two runs in 1995, respectively, and as of 1994, the global ocean contained 99 Pg C in RUN1 and 107 Pg C in RUN2 of anDIC, indicating that the model under the interannually varying forcing could take up 8.1% more anthropogenic carbon than the model under the climatological forcing. These values are within the range of other estimates based on observation and model simulation, while the estimates in RUN1 are near the low bound of other works. It is estimated that the variability of root mean square of the global air-sea anthropogenic carbon flux from the simulated monthly mean results of RUN2 with its seasonal cycle and long-term trend removed is 0.1 Pg C yr−1. The most distinct anomalies appear to be in the tropical Pacific Ocean and the Southern Ocean.