| Autor: |
Norgren, Matthew S., Wood, John, Schmidt, K. Sebastian, van Diedenhoven, Bastiaan, Stamnes, Snorre A., Ziemba, Luke D., Crosbie, Ewan C., Shook, Michael A., Kittelman, A. Scott, LeBlanc, Samuel E., Broccardo, Stephen, Freitag, Steffen, Reid, Jeffery S. |
| Předmět: |
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| Zdroj: |
Atmospheric Measurement Techniques Discussions; 9/28/2021, p1-36, 36p, 14 Graphs |
| Abstrakt: |
This study develops the use of spectral total and diffuse irradiance measurements, made from a prototype hyperspectral total-diffuse Sunshine Pyranometer (SPN-S), to retrieve layer fine-mode aerosol (τ푎푒푟) and total optical depths from airborne platforms. Additionally, we use spectral analysis in an attempt to partition the total optical depth it into its τ푎푒푟 and cirrus cloud optical depth (τ푐푙푑) components in the absence of coarse-mode aerosols. Two retrieval methods are developed: one leveraging information in the diffuse irradiance, and the other using spectral characteristics of the transmitted direct beam, with each approach best suited for specific cloud and aerosol conditions. SPN-S has advantages over traditional sunphotometer systems including no moving parts and a low cost. However, a significant drawback of the instrument is that it is unable to measure the direct beam irradiance as accurately as sun-photometers. To compensate for the greater measurement uncertainty of the radiometric irradiances these retrieval techniques employ ratioed inputs or spectral information to reduce output uncertainty. This analysis uses irradiance measurements from SPN-S and the Solar Spectral Flux Radiometer (SSFR) aboard the National Aeronautics and Space Administration's (NASA) P-3 aircraft during the 2018 deployment of the ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) campaign and the 2019 Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex) mission to quantify above-aircraft cirrus τ푐푙푑 and derive vertical profiles of layer τ푎푒푟. Validation of the τ푎푒푟 retrieval is accomplished by comparison with collocated measurements of direct solar irradiance made by the Sky-Scanning Sun-Tracking Atmospheric Research (4STAR) and in situ measurements of aerosol optical depth. For the aggregated 2018 ORACLES results, regression between the SPN-S based method and sun-photometer τ푎푒푟 values yield a slope of 0.96 with an 2 of 0.96, while the root-mean-square error (RMSE) is 3.0 × 10-2. When comparing the retrieved τ푎푒푟 to profiles of integrated in situ measurements of optical extinction, the slope, 푅2, and RMSE values for ORACLES results, regression between the SPN-S based method and sun-photometer τ푎푒푟 values yield a slope of 0.96 with an 푅2 of 0.96, while the root-mean-square error (RMSE) is 3.0 × 102. When comparing the retrieved t?????? to profiles of integrated in situ measurements of optical extinction, the slope, 푅2, and RMSE values for ORACLES are 0.90, 0.96, 3.4 × 10-2, and for CAMP2Ex are 0.94, 0.97, 3.4 × 10-2 respectively. This paper is a demonstration of methods for deriving cloud and aerosol optical properties in environments where both atmospheric constituents may be present. With improvements to the low-cost SPN-S radiometer instrument, it may be possible to extend these methods to a broader set of sampling applications, such as ground-based settings. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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