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  • Temporal and spatial heterogeneous distribution of tropospheric CO2 over China and its possible genesis
    Increase of greenhouse gas generated by human activities is one of the primary causes for global warming. Mid-troposphere CO2 data retrieved by AIRS (atmospheric infrared sounder), which had been running for 13 years, were validated with ground-based stations observations in this study. Then the spatial and temporal distribution and seasonal variations of CO2 concentration in China were studied with a variety of related data. The results show that there was a high CO2 concentration zone between 30 to 60 over the northern hemisphere, and a low concentration center over low latitudes from 15 degrees S to 15 degrees N, 140 degrees W eastward to 100 degrees E. AIRS CO2 products show good agreement with ground observations, with a 1.926 ppmv . a(-1) annual growth rate. Concentration of mid-troposphere CO2 was higher over northern China than over southern China, and there were four centers of high concentration located in the southwest of Northeast China, west Inner Mongolia, east and west Xinjiang, and low concentrations over Yunnan and the Tibetan area. There existed a significant seasonal CO2 variation with peak in spring, followed by winter and summer, and the lowest concentration occurs in autumn. The seasonal evolution of CO2 is closely related to the transport of the wind field, removal of precipitation and absorption of vegetation. more
  • A Case Study of the Stratospheric and Mesospheric Concentric Gravity Waves Excited by Thunderstorm in Northern China
    In this paper, the complete process in which a concentric gravity wave (CGW), excited by a tropospheric thunderstorm, propagated into the stratosphere and mesosphere in Northern China is investigated. A strong thunderstorm developed in the middle of the Inner Mongolia autonomous region on the night of 10th August 2013. The stratospheric temperature perturbation, caused by the CGW, was observed by the Atmospheric Infrared Sounder (AIRS) at 02:11 LT 11th August 2013. An all-sky OH imager at the Shuozhou station (39.8° N, 112.1° E), supported by the Meridian Space Weather Monitoring Project, measured the mesospheric CGW between 22:00 LT to 23:00 LT on the night. It was certified that both the stratospheric and mesospheric CGWs were triggered by the aforementioned thunderstorm, and the excitation source was calculated to be located at (40.59° N, 108.67° E) by employing the dispersion relation. The CGWs were excited in the initial stage of the thunderstorm. The temperature and wind field data obtained by SABER and meteoric radar, respectively, were used to evaluate the background properties of the respective propagation regions. The result shows that an obvious thermal duct structure, with a positive squared vertical wavenumber (m2) existed around the OH layer. more
  • Increased Frequency of Extreme Tropical Deep Convection: AIRS Observations and Climate Model Predictions
    Atmospheric Infrared Sounder (AIRS) data from the tropical oceans (30N‐30S) is used to derive the probability of the process resulting in Deep Convective Clouds (DCC) as function of the Sea Surface Temperature (SST). For DCC at or below the tropopause the onset temperature of this process shifts at the same rate as the increase in the mean SST. For tropopause overshooting DCC, which are associated with extreme rain events, the shift of the onset temperature is slower, causing their frequency to increase by about 21% per K of warming of the oceans. This sensitivity is not inconsistent with the sensitivity of the increase of extreme deep convective rain in the NCAR CAM5 model for a warmer SST. The mean of the 36 CMIP5 models predicts a 2.7 K warmer tropical SST by the end of this century, resulting in a 60% increases in the frequency of tropopause overshooting DCC. more
  • Changes in Global Tropospheric OH Expected as a Result of Climate Change Over the Last Several Decades
    The oxidizing capacity of the troposphere is controlled primarily by the abundance of hydroxyl radical (OH). The global mean concentration of tropospheric OH, [OH]TROP (the burden of OH in the global troposphere appropriate for calculating the lifetime of methane) inferred from measurements of methyl chloroform has remained relatively constant during the past several decades despite rising levels of methane that should have led to a decline. Here we examine other factors that may have affected [OH]TROP such as the changing values of stratospheric ozone, rising tropospheric H2O, varying burden of NOx (=NO+NO2), rising temperatures, and widening of the climatological tropics due to expansion of the Hadley cell. Our analysis suggests the positive trends in [OH]TROP due to H2O, NOx, and overhead O3, and tropical expansion are large enough (Δ [OH]TROP = +0.95 ± 0.18%/decade) to counter almost all of the expected decrease in [OH]TROP due to rising methane (Δ [OH]TROP = −1.01 ± 0.05%/decade) over the period 1980 to 2015, while variations in temperature contribute almost no trend (Δ [OH]TROP = −0.02 ± 0.02%/decade) in [OH]TROP. The approximated impact of Hadley cell expansion on [OH]TROP is also a small but not insignificant factor partially responsible for the steadiness of tropospheric oxidizing capacity over the past several decades, which free‐running models likely do not capture. more