Articles | Volume 16, issue 12
Research article
24 Jun 2016
Research article |  | 24 Jun 2016

Taklimakan Desert nocturnal low-level jet: climatology and dust activity

Jin Ming Ge, Huayue Liu, Jianping Huang, and Qiang Fu

Abstract. While nocturnal low-level jets (NLLJs) occur frequently in many parts of the world, the occurrence and other detailed characteristics of NLLJs over the Taklimakan Desert (TD) are not well known. This paper presents a climatology of NLLJs and coincident dust over the TD by analyzing multi-year ERA-Interim reanalysis and satellite observations. It is found that the ERA-Interim dataset can capture the NLLJs' features well by comparison with radiosonde data from two surface sites. The NLLJs occur in more than 60 % of nights, which are primarily easterly to east-northeasterly. They typically appear at 100 to 400 m above the surface with a speed of 4 to 10 m s−1. Most NLLJs are located above the nocturnal inversion during the warm season, while they are embedded in the inversion layer during the cold season. NLLJs above the inversion have a strong annual cycle with a maximum frequency in August. We also quantify the convective boundary layer (CBL) height and construct an index to measure the magnitude of the momentum in the CBL. We find that the magnitude of momentum in the lower atmosphere from the top of the surface layer to the top of mixed layer is larger for NLLJ cases than for non-NLLJ cases, and in the warm season the downward momentum transfer process is more intense and rapid. The winds below the NLLJ core to the desert surface gain strength in summer and autumn, and these summer and autumn winds are coincident with an enhancement of aerosol optical depth. This indicates that the NLLJ is an important mechanism for dust activity and transport during the warm season over the Taklimakan.

Short summary
Nocturnal low-level jet (NLLJ), which refers to a narrow zone of strong winds, occurs frequently over the Taklimakan Desert. It is found that the NLLJ contains more momentum than without NLLJ, and the downward momentum transfer process is more intense and rapid in the warm season. The coincidence of the larger surface winds during NLLJ days with an enhancement of aerosol optical depth indicates that the NLLJ is an important mechanism for dust emission and transport over this region.
Final-revised paper