Impact of tropospheric nitrogen dioxide on the regional radiation budget

A P Vasilkov,L Oreopoulos,S Platnick,E A Celarier,P Veefkind,J Joiner,J F Gleason,R J D Spurr,E Bucsela

doi:10.5194/acp-9-6389-2009

Abstract

Abstract. Following the launch of several satellite ultraviolet and visible spectrometers including the Ozone Monitoring Instrument (OMI), much has been learned about the global distribution of nitrogen dioxide (NO2). NO2, which is mostly anthropogenic in origin, absorbs solar radiation at ultraviolet and visible wavelengths. We parameterized NO2 absorption for fast radiative transfer calculations. Using this parameterization with cloud, surface, and NO2 information from different sensors in the NASA A-train constellation of satellites and NO2 profiles from the Global Modeling Initiative (GMI), we compute the global distribution of net atmospheric heating (NAH) due to tropospheric NO2 for January and July 2005. The globally-averaged NAH values due to tropospheric NO2 are very low: they are about 0.05 W/m2. While the impact of NO2 on the global radiative forcing is small, locally it can produce instantaneous net atmospheric heating of 2–4 W/m2 in heavily polluted areas. We assess the impact of clouds and find that they reduce the globally-averaged NAH values by 5–6% only. However, because most of NO2 is contained in the boundary layer in polluted regions, the cloud shielding effect can significantly reduce the net atmospheric heating due to tropospheric NO2 (up to 50%). We examine the effect of diurnal variations in NO2 emissions and chemistry on net atmospheric heating and find only a small impact of these on the daily-averaged heating (11–14% at the most). We also examine the sensitivity of NO2 absorption to various geophysical conditions. Effects of the vertical distributions of cloud optical depth and NO2 on net atmospheric heating and downwelling radiance are simulated in detail for various scenarios including vertically-inhomogeneous convective clouds observed by CloudSat. The maximum effect of NO2 on downwelling radiance occurs when the NO2 is located in the middle part of the cloud where the optical extinction peaks.

Highlights

The absorption of incoming solar and outgoing terrestrial radiation by trace gases is one of the key factors in the Earth’s radiative budget and plays a leading role in climate change (Hansen et al, 2007)
Little attention has been paid to nitrogen dioxide (NO2), because its effect on the global radiative budget, the radiative forcing, is small
On a local scale, enhanced NO2 in polluted areas can change the partitioning of absorbed solar radiation between the atmosphere and surface; it produces atmospheric heating in the troposphere and contributes to dimming at the surface

Summary

Introduction

The absorption of incoming solar and outgoing terrestrial radiation by trace gases is one of the key factors in the Earth’s radiative budget and plays a leading role in climate change (Hansen et al, 2007). Vasilkov et al.: Satellite-derived radiative impact of tropospheric NO2 peak absorption of downwelling radiation by NO2 was 5–. We compute the global distribution of the net atmospheric heating (NAH) due to tropospheric NO2 with an emphasis on polluted areas. Eral data sets from the NASA A-train constellation of afternoon satellites flying within fifteen minutes of each other near 13:30 local solar time. These include cloud and surface properties from the NASA Aqua Moderate Resolution Imag-. 4, we present computed global and regional distributions of the tropospheric NO2 NAH based on NO2 amounts derived from OMI observations and cloud data taken from MODIS and OMI retrievals. The transmission function averaged over a spectral band is first calculated from

Parameterization of NO2 absorption

Global NO2 net atmospheric heating calculations

OMI NO2 retrievals

Findings

Cloud data sets