Numerical Simulations of Spatial Distributions and Diurnal Variations of Low-Level Jets in China during Early Summer

Abstract

The detailed spatial distributions and diurnal variations of low-level jets (LLJs) during early summer (May–July) in China are documented using 2006–11 hourly model data from the Weather Research and Forecasting (WRF) Model with a 9-km horizontal resolution. It was found that LLJs frequently occur in the following regions of China: the Tarim basin, northeastern China, the Tibetan Plateau (TP), and southern China. The LLJs over China are classified into two types: boundary layer jets (BLJs, below 1 km) and synoptic-system-related LLJs (SLLJs, within 1–4 km). The LLJs in the Tarim basin and the TP are mainly BLJs. The SLLJs over southern China and northeastern China are associated with the mei-yu front and northeast cold vortex (NECV), respectively. The BLJs in all regions show pronounced diurnal variations with maximum occurrences at nighttime or in the early morning, whereas diurnal variations of SLLJs vary, depending on the location. From the analysis of model data, the diurnal variation of BLJs is mainly caused by inertial oscillation at nighttime and vertical mixing in the boundary layer during daytime. Over northeastern China, SLLJ occurrences show little diurnal variation. Over southern China, two diurnal modes of SLLJs, propagation and stationary, exist and have seasonal variations, which is generally consistent with diurnal variations of precipitation.

The Controlling Role of Boundary Layer Inertial Oscillations in Meiyu Frontal Precipitation and Its Diurnal Cycles Over China

“…In general, the Blackadar inertial oscillation theory explains better the behaviors of the Great Plains LLJ than the Holton theory, although most recently a unified theory has been proposed that combines the two effects (Shapiro et al, ), resulting in a better fit of the theoretical prediction to observations. In comparison, the boundary layer LLJ and its diurnal oscillations over China have been studied less, with Du and Zhang (); Du et al (); Du, Chen, and Zhang (); and Du, Rotunno, and Zhang () being some of the few examples. These studies also suggest that inertial oscillations play important roles.…”

Low‐Level Jets Over the Bohai Sea and Yellow Sea: Climatology, Variability, and the Relationship With Regional Atmospheric Circulations

“…There have been extensive studies on LLJs over regions worldwide including, but not limited to, North America (Higgins et al, ), Europe (Soares et al, ), South America (Marengo et al, ), and Asia (Du et al, ). Over the land, the most renowned LLJs that have been intensively studied are the Great Plains LLJs over North America (Blackadar, ; Higgins et al, ; Parish & Oolman, ), which are most frequent during the warm seasons from April to October and are greatly influenced by the sloping terrain of the Rocky Mountains.…”

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

“…Rife et al (2010) examined the Tarim Basin NLLJ, but they only focused on its diurnal variation for July. Du et al (2014) simulated diurnal variations in Tarim Basin NLLJs during early summer from 2006 to 2011 by using the Weather Research and Forecasting (WRF) model. In this paper, we present an NLLJ detection algorithm and show the climatology and seasonal variation in NLLJ over the Taklimakan by using the ERA-Interim reanalysis data.…”