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  • Verification of satellite ozone/temperature profile products and ozone effective height/temperature over Kunming, China
    Ozonesonde data from November 2013 to April 2015 over Kunming, China are used to verify ozone and temperature profile retrievals from two spaceborne instruments, the version 4.2 product from the Microwave Limb Sounder (MLS) on the NASA Aura satellite and the version 6.0 product from the Atmospheric Infrared Sounder (AIRS) on the NASA Aqua satellite. We calculated and compared the ozone effective height Heff and effective temperature Teff, which are two important parameters in ground-based total ozone retrieval through the use of various profile datasets. This is used to verify the accuracy of the operative values (Heff(0) = 23 km, Teff(0) = -46.3 °C (or -45 °C)) from the World Meteorological Organization. The results show that the deviation of MLS and AIRS ozone profiles from ozone sounding data has significant oscillation and scatter in the upper troposphere and lower stratosphere. The average difference of MLS at 82.5 hPa is (80.5 ± 65.1) %, and that of AIRS at 70 and 100 hPa are (105.6 ± 74.9) % and (107.0 ± 67.8) %, respectively. The two satellite temperature profiles have differences within ±3 °C and can effectively describe the vertical distribution and variation of temperature. When calculating the Heff and Teff, upper stratospheric data missing from the sounding data must be filled in by the satellite profile data; otherwise the calculated results will show large errors of 3.2 km and 3.3 °C. The Heff and Teff at Kunming are respectively 24.36 to 25.51 km and -48.3 to -43.6 °C. The operational Heff and Teff used at Kunming ozone observation station clearly do not conform to the actual situation and must be corrected. more
  • The Atmospheric Infrared Sounder Obs4MIPs Version 2 Data Set
    The Atmospheric Infrared Sounder (AIRS) Obs4MIPs (Observations for Model Intercomparison Projects) Version 2 data set includes monthly mean tropospheric air temperature, specific humidity, and relative humidity for each calendar month from September 2002 to September 2016, on a global 1° × 1° latitude‐longitude spatial grid and on the Coupled Model Intercomparison Project eight mandatory vertical pressure levels from 1,000 to 300 hPa. It also includes standard error and number of observations, for an estimate of AIRS data retrieval error and sampling uncertainty. Three new technical notes describe the data set. This data set is designed for Coupled Model Intercomparison Project climate model evaluation and has been published at Earth System Grid Federation data centers since April 2018. It adds new monthly mean tropospheric relative humidity data to Obs4MIPs and updates and extends the monthly mean tropospheric air temperature and specific humidity data in AIRS Obs4MIPs Version 1 data set. The data source for this data set is the AIRS Version 6 Level 3 standard monthly mean air temperature, specific humidity, and relative humidity data products in the “TqJoint” grids from the AIRS and Advanced Microwave Sounding Unit A combined physical retrievals. This paper documents this data set in terms of motivation for this data set, data description, data origin and processing procedures, major improvements from the previous version, and caveats for its use in climate model evaluation. more
  • Atmospheric Moisture Measurements Explain Increases in Tropical Rainfall Extremes
    Anthropogenic climate change is increasing extreme rainfall as a result of an increased water-holding capacity of the atmosphere due to higher temperatures. However, observed rainfall-temperature scaling relationships often differ from the theorized increases in moisture-holding capacity. This discrepancy is most evident in the tropics, where higher surface temperatures show a marked decrease in extreme rainfall intensity despite observed increases in extreme rainfall. Here we use atmospheric moisture measurements from the National Aeronautics and Space Administration's Atmospheric Infrared Sounder with surface data to investigate the tropical rainfall-temperature scaling relationship. We show rainfall intensity scales positively with integrated water vapor in all regions. Further, integrated water vapor does not consistently scale positively with surface air temperature and its dependence on background temperature offers a physical explanation for the apparent negative scaling. We conclude that the inconsistent relationship between surface air temperature and moisture is the reason for the “apparent” negative scaling consistently found in the tropics. more
  • Long-range-transported Canadian smoke plumes in the lower stratosphere over northern France
    Long-range-transported Canadian smoke layers in the stratosphere over northern France were detected by three lidar systems in August 2017. The peaked optical depth of the stratospheric smoke layer exceeds 0.20 at 532 nm, which is comparable with the simultaneous tropospheric aerosol optical depth. The measurements of satellite sensors revealed that the observed stratospheric smoke plumes were transported from Canadian wildfires after being lofted by strong pyro-cumulonimbus. Case studies at two observation sites, Lille (lat 50.612, long 3.142, 60 m a.s.l.) and Palaiseau (lat 48.712, long 2.215, 156 m a.s.l.), are presented in detail. Smoke particle depolarization ratios are measured at three wavelengths: over 0.20 at 355 nm, 0.18-0.19 at 532 nm, and 0.04-0.05 at 1064 nm. The high depolarization ratios and their spectral dependence are possibly caused by the irregular-shaped aged smoke particles and/or the mixing with dust particles. Similar results are found by several European lidar stations and an explanation that can fully resolve this question has not yet been found. Aerosol inversion based on lidar 2 alpha + 3 beta data derived a smoke effective radius of about 0.33 mu m for both cases. The retrieved single-scattering albedo is in the range of 0.8 to 0.9, indicating that the smoke plumes are absorbing. The absorption can cause perturbations to the temperature vertical profile, as observed by ground-based radiosonde, and it is also related to the ascent of the smoke plumes when exposed in sunlight. A direct radiative forcing (DRF) calculation is performed using the obtained optical and microphysical properties. The calculation revealed that the smoke plumes in the stratosphere can significantly reduce the radiation arriving at the surface, and the heating rate of the plumes is about 3.5 K day(-1). The study provides a valuable characterization for aged smoke in the stratosphere, but efforts are still needed in reducing and quantifying the errors in the retrieved microphysical properties as well as radiative forcing estimates. more