Preliminary Sensitivity Study of Aerosol Layer Height From Synthetic Multiangle Polarimetric Remote Sensing Measurements

Abstract

Abstract. Many previous studies have shown that multiangle, multispectral polarimetric remote sensing can provide valuable information on aerosol microphysical and optical properties, in which the aerosol layer height (ALH) is an important parameter but with less studies, especially in the near-ultraviolet (near-UV) and visible (VIS) wavelength bands. Based on the optimal estimation (OE) theory and information content analysis method, we focus on the sensitivity study of ALH with the synthetic data in the near-UV and VIS wavelength in the range of 410–865 nm, and further to assess the capability of multiangle intensity and polarization measurements for the retrieval of ALH. Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) has been used as the forward model to simulate the intensity and polarized radiance at the top of atmosphere (TOA), as well as the Jacobians of TOA results with respective to corresponding parameters. The degree of freedom for signal (DFS) and a posteriori error are introduced to quantity the information content of ALH from the intensity and polarization measurements, respectively. By assuming the surface type, aerosol model, aerosol loads, prior errors and observation geometries, the sensitivity of ALH has been preliminarily investigated. The sensitivity study results show that the near-UV and polarization measurements are the important source of information content for the aerosol height retrieval in satellite remote sensing.

A Comprehensive Analysis of Ultraviolet Remote Sensing for Aerosol Layer Height Retrieval from Multi-Angle Polarization Satellite Measurements

“…In Section 4.2, we analyze the ability of MAPMU to detect the aerosol layer height for typical cases and show the impact of uncertainty for aerosol models. However, previous studies have shown that the aerosol vertical distribution is also affected by the aerosol model parameters (AOD, H), while the impact of these parameters generally appears to be similar in different aerosol types [7,29]. Therefore, in this section, we test the changes in ALH information under different aerosol optical depth conditions (AOD is from 0.2 to 1.0) and scale height conditions including near-ground aerosols and transported aerosols above the boundary layer (H is from 1 km to 5 km) for the vegetation surface.…”

“…Using Equation ( 15), we used the specified constant measurement errors from the previous section to calculate the DFS results resulting from various model errors. Previous research has shown that the DFS of the aerosol layer height will be affected by the aerosol types and has shown the differences, but the impact of AOD generally appear similar in different aerosol types [7,29]. Therefore, we concentrated on AOD = 0.6 and scale height = 2 km as a demonstration.…”

“…A theoretical analysis employing every form of aerosol is a difficult and unrealistic method. In order to simplify this method, previous studies have often analyzed some typical aerosol types (such as fine-dominated and coarse-dominated types) [7,28,34]. We hope to use a more realistic aerosol model classification while building a more sophisticated ALH retrieval framework for the Chinese region in order to explore the ability of UV multi-angle polarization measurements to undergo ALH retrieval for different aerosol types.…”

“…It also depends on whether the measurement can meet the profile model parameters which are in the state vectors to solve at the same time. In the simulation, we assume that the profile of the aerosol extinction coefficient follows an exponential-decay profile, which is often used in atmospheric correction algorithms and can be written in the form of [7,32,36]:…”

“…ALH is commonly used in model calculation, while in the passive remote sensing measurements, it can be always be replaced by planetary boundary layer height (PBLH). The planetary boundary layer is the lowest layer of the atmosphere and, which contains the vast majority of aerosols of the low troposphere [6,7]. At the same time, the height information on smoke, volcanic, and dust aerosols can provide the initial conditions for the modeling of their emissions and the physics of plume formation [8][9][10].…”