scholarly journals Variation of boundary layer heights and eddy diffusivities over dry and moist convective regions of monsoon trough during different phases of monsoon

MAUSAM ◽  
2021 ◽  
Vol 50 (2) ◽  
pp. 181-186
Author(s):  
B. PADMANABHAMURTY ◽  
INDU JAIN
Keyword(s):  
Boundary Layer ◽  
Indirect Method ◽  
Direct Method ◽  
Sonic Anemometer ◽  
Monsoon Trough ◽  
Eddy Correlation ◽  
Diffusivity Coefficient ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Convective Region

Temperature, wind, and humidity data at 6 levels over meteorological towers at Kharagpur and Jodhpur and fast data at Jodhpur (Sonic anemometer at 4m and Gill anemometer  15 m) and Kharagpur (Sonic anemometer at 8m and Gill anemometer at 15m) were analysed. Diurnal variation of boundary layer heights and eddy diffusivity coefficient of moment, heat and moisture at dry convective region Jodhpur (26° N, 73°E) and moist convective region Kharagpur (22.3°N, 87.2°E) of monsoon trough during onset of monsoon, mid-monsoon and end-monsoon phases of the Indian southwest monsoon are studied using micro meteorological tower data. Boundary layer height is computed by eddy correlation (direct method) and profile method {indirect method). Indirect method underestimates the boundary layer height.

scholarly journals Estimating the atmospheric boundary layer height over sloped, forested terrain from surface spectral analysis during BEARPEX

2010 ◽  
Vol 10 (11) ◽  
pp. 25759-25801 ◽  
Author(s):  
W. Choi ◽  
I. C. Faloona ◽  
M. McKay ◽  
A. H. Goldstein ◽  
B. Baker
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Sierra Nevada ◽  
Sonic Anemometer ◽  
Coniferous Forest ◽  
Power Spectra ◽  
Nocturnal Boundary Layer ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Stable Conditions

Abstract. In this study the atmospheric boundary layer (ABL) height (zi) over complex, forested terrain is estimated based on the power spectra and the integral length scale of horizontal winds obtained from a three-axis sonic anemometer during the BEARPEX (Biosphere Effects on Aerosol and Photochemistry) Experiment. The zi values estimated with this technique showed very good agreement with observations obtained from balloon tether sonde (2007) and rawinsonde (2009) measurements under unstable conditions (z/L < 0) at the coniferous forest in the California Sierra Nevada. The behavior of the nocturnal boundary layer height (h) and power spectra of lateral winds and temperature under stable conditions (z/L > 0) is also presented. The nocturnal boundary layer height is found to be fairly well predicted by a recent interpolation formula proposed by Zilitinkevich et al. (2007), although it was observed to only vary from 60–80 m during the experiment. Finally, significant directional wind shear was observed during both day and night with winds backing from the prevailing west-southwesterlies in the ABL (anabatic cross-valley circulation) to consistent southerlies in a layer ~1 km thick just above the ABL before veering to the prevailing westerlies further aloft. We show that this is consistent with the forcing of a thermal wind driven by the regional temperature gradient directed due east in the lower troposphere.

scholarly journals Estimating the atmospheric boundary layer height over sloped, forested terrain from surface spectral analysis during BEARPEX

2011 ◽  
Vol 11 (14) ◽  
pp. 6837-6853 ◽  
Author(s):  
W. Choi ◽  
I. C. Faloona ◽  
M. McKay ◽  
A. H. Goldstein ◽  
B. Baker
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Sierra Nevada ◽  
Sonic Anemometer ◽  
Power Spectra ◽  
Nocturnal Boundary Layer ◽  
Wind Component ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Stable Conditions

Abstract. The atmospheric boundary layer (ABL) height (zi) over complex, forested terrain is estimated based on the power spectra and the integral length scale of cross-stream winds obtained from a three-axis sonic anemometer during the two summers of the BEARPEX (Biosphere Effects on Aerosol and Photochemistry) Experiment. The zi values estimated with this technique show very good agreement with observations obtained from balloon tether sondes (2007) and rawinsondes (2009) under unstable conditions (z/L < 0) at the coniferous forest in the California Sierra Nevada. On the other hand, the low frequency behavior of the streamwise upslope winds did not exhibit significant variations and was therefore not useful in predicting boundary layer height. The behavior of the nocturnal boundary layer height (h) with respect to the power spectra of the v-wind component and temperature under stable conditions (z/L > 0) is also presented. The nocturnal boundary layer height is found to be fairly well predicted by a recent interpolation formula proposed by Zilitinkevich et al. (2007), although it was observed to only vary from 60–80 m during the 2009 experiment in which it was measured. Finally, significant directional wind shear was observed during both day and night soundings. The winds were found to be consistently backing from the prevailing west-southwesterlies within the ABL (the anabatic cross-valley circulation) to southerlies in a layer ~1–2 km thick just above the ABL before veering to the prevailing westerlies further aloft. This shear pattern is shown to be consistent with the forcing of a thermal wind driven by the regional temperature gradient directed east-southeast in the lower troposphere.

scholarly journals Technical note: Boundary layer height determination from Lidar for improving air pollution episode modelling: development of new algorithm and evaluation

2017 ◽  
Author(s):  
Ting Yang ◽  
Zifa Wang ◽  
Wei Zhang ◽  
Alex Gbaguidi ◽  
Nubuo Sugimoto ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
High Performance ◽  
Accurate Determination ◽  
Technical Note ◽  
Strong Increase ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Retrieval Algorithms ◽  
The Impact

Abstract. Predicting air pollution events in low atmosphere over megacities requires thorough understanding of the tropospheric dynamic and chemical processes, involving notably, continuous and accurate determination of the boundary layer height (BLH). Through intensive observations experimented over Beijing (China), and an exhaustive evaluation existing algorithms applied to the BLH determination, persistent critical limitations are noticed, in particular over polluted episodes. Basically, under weak thermal convection with high aerosol loading, none of the retrieval algorithms is able to fully capture the diurnal cycle of the BLH due to pollutant insufficient vertical mixing in the boundary layer associated with the impact of gravity waves on the tropospheric structure. Subsequently, a new approach based on gravity wave theory (the cubic root gradient method: CRGM), is developed to overcome such weakness and accurately reproduce the fluctuations of the BLH under various atmospheric pollution conditions. Comprehensive evaluation of CRGM highlights its high performance in determining BLH from Lidar. In comparison with the existing retrieval algorithms, the CRGM potentially reduces related computational uncertainties and errors from BLH determination (strong increase of correlation coefficient from 0.44 to 0.91 and significant decrease of the root mean square error from 643 m to 142 m). Such newly developed technique is undoubtedly expected to contribute to improve the accuracy of air quality modelling and forecasting systems.

On stable boundary-layer height estimation using backscatter lidar data and variance processing

2021 ◽  
Author(s):  
Marcos Paulo Araujo da Silva ◽  
Constantino Muñoz-Porcar ◽  
Umar Saeed ◽  
Francesc Rey ◽  
Maria Teresa Pay ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Stable Boundary Layer ◽  
Adaptive Estimation ◽  
Microwave Radiometer ◽  
Minimum Variance ◽  
Initial Guess ◽  
Layer Height ◽  
Stable Boundary ◽  
Boundary Layer Height ◽  
Temporal Variance

&lt;p&gt;This study describes a method to estimate the nocturnal stable boundary layer height (SBLH) by means of lidar observations. The method permits two approaches which yield independent retrievals through either spatial or temporal variance vertical profiles of the attenuated backscatter. Then, the minimum variance region (MVR) on this profile is identified. Eventually, when multiple MVRs are detected, a temperature-based SBLH estimation derived from radiosonde, launched within the searching time, is used to disambiguate the initial guess. In order to test the method, two study cases employing lidar-ceilometer (Jenoptik CHM 15k Nimbus) measurements are investigated. Temperature-based estimates from a collocated microwave radiometer permitted validation, using either temporal or spatial backscatter variances. The dataset was collected during the HD(CP)2 Observational Prototype Experiment (HOPE) [1]. &amp;#160;&amp;#160;&lt;/p&gt;&lt;p&gt;[1] U. Saeed, F. Rocadenbosch, and S. Crewell, &amp;#8220;Adaptive Estimation of the Stable Boundary Layer Height Using Combined Lidar and Microwave Radiometer Observations,&amp;#8221; IEEE Trans. Geosci. Remote Sens., 54(12), 6895&amp;#8211;6906 (2016), DOI: 10.1109/TGRS.2016.2586298.&lt;/p&gt;&lt;p&gt;[2] U. L&amp;#246;hnert, J. H. Schween, C. Acquistapace, K. Ebell, M. Maahn, M. Barrera-Verdejo, A. Hirsikko, B. Bohn, A. Knaps, E. O&amp;#8217;Connor, C. Simmer, A. Wahner, and S. Crewell, &amp;#8220;JOYCE: J&amp;#252;lich Observatory for Cloud Evolution,&amp;#8221; Bulletin of the American Meteorological Society, 96(7), 1157-1174 (2015). DOI: 10.1175/BAMS-D-14-00105.1&lt;/p&gt;

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