Impacts of the Saharan air layer on the physical properties of the Atlantic tropical cyclone cloud systems: 2003–2019
It is generally known that the tropical cyclone (TC) cloud systems (TCCS) in the North Atlantic region frequently occur during boreal summer, while the Saharan dust outbreaks concurrently. The Sahara air layer (SAL), an elevated layer containing Saharan dry air and mineral dust, makes crucial impact...
| Main Authors: | , |
|---|---|
| Format: | Text |
| Language: | English |
| Published: |
2021
|
| Subjects: | |
| Online Access: | https://doi.org/10.5194/acp-2021-462 https://acp.copernicus.org/preprints/acp-2021-462/ |
| Summary: | It is generally known that the tropical cyclone (TC) cloud systems (TCCS) in the North Atlantic region frequently occur during boreal summer, while the Saharan dust outbreaks concurrently. The Sahara air layer (SAL), an elevated layer containing Saharan dry air and mineral dust, makes crucial impacts on the generation and evolution of TCs. However, the effects of SAL on the physical (macro and micro) characteristics of the Atlantic TCCS have not been well constrained, and the interaction mechanisms between them still need further investigation. In this study, our primary interest is to distinguish the various effects of SAL on different intensities of TCs, and further find out the probable causes of the varied feedback. Therefore, we attempt to identify whether and how the effects of the SAL play a positive or negative role on the TCCS, and to draw a qualitative conclusion of how SAL affects the various intensities of the TCs. This paper focuses on the 70 TC samples from July to September in the years of 2003–2019 to investigate the physical effects of SAL on three intensities of TCs, i.e.: the tropical depression (TD), tropical storm (TS), and hurricane (HU). The results show that SAL has a positive impact on the macro properties of HU but significantly suppresses the TD. It appears that the SAL attributes little to the variation of ice cloud effective radius (CER i ) for TS, whereas CER i changes significantly and differentially for TD and HU. When affected by SAL, the probability density function (PDF) curve of CER i generally shifts to the smaller value for TD, but the PDF curve becomes flatten for HU. Our analysis indicates that the various responses of TCCS to SAL are determined by the combined effects of dry air masses, the dust aerosols as ice nuclei, as well as the thermodynamic and moisture conditions. Based on the observation data analysis, a concept scheme description has been concluded to deepen our recognition of the effects of SAL on the TCCS. |
|---|