Study of boundary layer characteristics during the landfalling of a Nisarga cyclone

One of the most important parameters in meteorology is the mean wind profile in the tropical cyclone boundary layer.The vertical profile of wind speed and wind direction were measured during the period of the Nisarga cyclone from May 31st,2020,to June 5th,2020,using the newly installed Phased Array Doppler Sodar system at the Center for Space and Atmospheric Science(CSAS),Sanjay Ghodawat University,Kolhapur(16.74◦N,74.37◦E;near India's western coast).Our analysis revealed that the maximum mean wind speed was 17 m/s on June 3,2020,at 10:00 IST.It also shows the change in wind direction from southwest to southeast on June 2 and 3,2020.Daily high-resolution reanalysis data in the domain,0–25◦N,65–110◦E,during the period from May 31st to June 5th,2020,revealed the variation of the atmospheric pressure of the Nisarga cyclone from 1000 to 1008 hPa,sea surface temperature(SST)between 30◦C and 31◦C,outgoing longwave radiation(OLR)between 100 and 240 Wm-2,wind speed between 3 and 15 m/s,and low values of vertical wind shear(VWS)were observed to the north of Nisarga track.These observations may provide more insights for the study of boundary layer turbulence during cyclonic activities.

On the atmospheric movement and the imbalance of observed and calculated energy in the surface layer

Based on existing researches,here we theoretically summarized the characteristics of the atmospheric movement and turbulent transport of energy and substance in the surface layer as well as the ideal and the actual models for the turbulent transport.Then,using the data observed with eddy covariance at the semiarid climate and environment monitoring station(SACOL) in Lanzhou University from May to October during four consecutive years(September 2006-August 2010),we conducted a detailed analysis of the turbulent transport in the surface layer,through introducing the relative vertical turbulence intensity to characterize the turbulence strength,RIw=wn(wn+U),and also by adopting the method for controlling data quality at different levels.Our conclusions are:(1) The turbulent transport of energy and substance in the surface layer must obey the law of conservation of energy and the law of conservation of matter,the observed and calculated energy in the surface layer must be balanced,or closed in theory,but the actual observed and calculated energy just approximates the ideal in some degree and is difficult to achieve the energy balance.(2) The energy closure rate depends much on the atmospheric state in the surface layer,and the energy closure rate increases generally with the relative vertical turbulence intensity.(3) By the way of controlling data quality at different levels,it is found that the degree of data quality control can affect the closure rate,but it does not change the fact that the energy closure rate depends on the atmospheric state.(4) The calculation method of surface soil heat flux can affect energy closure rate,but does not change its dependence on the atmospheric state.