Radiative Forcing Estimation of Aerosols at an Urban Site near the Thar Desert Using Ground-Based Remote Sensing Measurements

  The focus of present study is to quantify the radiation budget of aerosols over Jaipur (Northwestern, India) from 2011 to 2015. The Aerosol radiative forcing (ARF) has been determined for shortwave spectrum (0.3–3.0 µm) individually for the top of the atmosphere (TOA), bottom of the atmosphere (BOA) and within the atmosphere (ATM) over study region. Santa Barbara DISORT Atmospheric Radiative Transfer model (SBDART) is used to simulate the aerosols radiative effect.  The inter-annual monthly average of ARF at TOA during 2011–2015 is found between –11.40 to –5.60 W m–2, while the ARF at BOA is found to be between –32.2 to –22.49 W m–2. Likewise, the ARF within the atmosphere (ATM) comes between 14.04 to 22.47 W m–2 over Jaipur. The SBDART model is run discretely for Dust period (DSP) and non-Dust Period (NDP) during the year 2012 to inspect the change in ARF during extreme events over the Jaipur site. During DSP, the net TOA and BOA forcing are found in the range –20.71 to –16.81 W m–2 and –45.15 to –39.6 W m–2, respectively, and net ATM forcing varies in the range 22.7 to 24.4 W m–2. For the NDP, the corresponding value varies in the range –10.1 to –6.6 W m–2 and –23.6 to –22.3 W m–2. The net ATM forcing during NDP is between 12.2 to 17.05 W m–2. The value of BOA increases more than ~67% during DSP than NDP. The more increase (–ve) in surface forcing represents the cooling of the surface during DSP. The results depict that dust over Jaipur in the vicinity of the Thar Desert is scattering in nature with high value (> 0.95) of SSA. The scattering is mostly high during summer and low in winter.