Processing Doppler Lidar and Cloud Radar Observations for Analysis of Convective Mass Flux Parameterizations Using DYNAMO Direct Observations

AbstractMass flux is a key quantity in parameterizations of shallow convection. To estimate the shallow convective mass flux as accurately as possible, and to test these parameterizations, observations of this parameter are necessary. In this study, we show how much the mass flux varies and how this can be used to test factors that may be responsible for its variation. Therefore, we analyze long term Doppler radar and Doppler lidar measurements at the Barbados Cloud Observatory over a time period of 30 months, which results in a mean mass flux profile with a peak value of 0.03 kg m−2 s−1 at an altitude of ~730 m, similar to observations from Ghate et al. (2011) at the Azores Islands. By combining Doppler radar and Doppler lidar measurements, we find that the cloud base mass flux depends mainly on the cloud fraction and refutes an idea based on large eddy simulations, that the velocity scale is in major control of the shallow cumulus mass flux. This indicates that the large scale conditions might play a more important role than what one would deduce from simulations using prescribed large-scale forcings.

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Convective mass-flux from long term radar reflectivities over Darwin, Australia

10.1002/essoar.10506524.1 ◽

2021 ◽

Author(s):

Alessandro Carlo Maria Savazzi ◽

Christian Jakob ◽

Pier Siebesma

Keyword(s):

Mass Flux ◽

Convective Mass Flux

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First Doppler lidar and cloud radar measurements of orographic convection initiation from a mountain observatory in the Al Hajar Mountains of the United Arab Emirates.

10.5194/egusphere-egu21-9715 ◽

2021 ◽

Author(s):

Oliver Branch ◽

Andreas Behrendt ◽

Osama Alnayef ◽

Florian Späth ◽

Thomas Schwitalla ◽

...

Keyword(s):

United Arab Emirates ◽

Sea Breeze ◽

Doppler Lidar ◽

Cloud Seeding ◽

Low Level ◽

Cloud Radar ◽

Orographic Convection ◽

Radar Measurements ◽

Convection Initiation ◽

Convective Cells

We present exciting Doppler lidar and cloud radar measurements from a high-vantage mountain observatory in the hyper-arid United Arab Emirates (UAE) - initiated as part of the UAE Research Program for Rain Enhancement Science (UAEREP). The observatory was designed to study the clear-air pre-convective environment and subsequent convective events in the arid Al Hajar Mountains, with the overarching goal of improving understanding and nowcasting of seedable orographic clouds. During summer in the Al Hajar Mountains (June to September), weather processes are often complex, with summer convection being initiated by several phenomena acting in concert, e.g., interaction between sea breeze and horizontal convective rolls. These interactions can combine to initiate sporadic convective storms and these can be intense enough to cause flash floods and erosion. Such events here are influenced by mesoscale phenomena like the low-level jet and local sea breeze, and are constrained by larger-scale synoptic conditions.The Doppler lidar and cloud radar were employed for approximately two years at a high vantage-point to capture valley wind flows and observe convective cells. The instruments were configured to run synchronized polar (PPI) scans at 0&#176;, 5&#176;, and 45&#176; elevation angles and vertical cross-section (RHI) scans at 0&#176;, 30&#176;, 60, 90&#176;, 120&#176;, and 150&#176; azimuth angles. Using this imagery, along with local C-band radar and satellite data, we were able to identify and analyze several convective cases. To illustrate our results, we have selected two cases under unstable conditions - the 5 and 6 September 2018. In both cases, we observed areas of low-level convergence/divergence, particularly associated with wind flow around a peak 2 km to the south-west of the observatory. The extension of these deformations are visible in the atmosphere to a height of 3 km above sea level. Subsequently, we observed convective cells developing at those approximate locations &#8211; apparently initiated because of these phenomena. The cloud radar images provided detailed observations of cloud structure, evolution, and precipitation. In both convective cases, pre-convective signatures were apparent before CI, in the form of convergence, wind shear structures, and updrafts.These results have demonstrated the value of synergetic observations for understanding orographic convection initiation, improvement of forecast models, and cloud seeding guidance. The manuscript based on these results is now the subject of a peer review (Branch et al., 2021).&#160;Branch, O., Behrendt, Andreas Alnayef, O., Sp&#228;th, F., Schwitalla, Thomas, Temimi, M., Weston, M., Farrah, S., Al Yazeedi, O., Tampi, S., Waal, K. de and Wulfmeyer, V.: The new Mountain Observatory of the Project &#8220;Optimizing Cloud Seeding by Advanced Remote Sensing and Land Cover Modification (OCAL)&#8221; in the United Arab Emirates: First results on Convection Initiation, J. Geophys. Res.&#160; Atmos., 2021. In review (submitted 23.11.2020).

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Comments on "Research on Retrieval of Atmospheric Temperature and Humidity Profiles from combined Ground-based Microwave Radiometer and Cloud Radar Observations"

10.5194/amt-2016-286-rc2 ◽

2016 ◽

Author(s):

Anonymous

Keyword(s):

Microwave Radiometer ◽

Atmospheric Temperature ◽

Radar Observations ◽

Cloud Radar ◽

Temperature And Humidity ◽

Humidity Profiles

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Analysis of Convective Transport and Parameter Sensitivity in a Single Column Version of the Goddard Earth Observation System, Version 5, General Circulation Model

Journal of the Atmospheric Sciences ◽

10.1175/2008jas2694.1 ◽

2009 ◽

Vol 66 (3) ◽

pp. 627-646 ◽

Cited By ~ 26

Author(s):

L. E. Ott ◽

J. Bacmeister ◽

S. Pawson ◽

K. Pickering ◽

G. Stenchikov ◽

...

Keyword(s):

Mass Flux ◽

General Circulation ◽

Parameter Sensitivity ◽

Convective Transport ◽

Trace Gas ◽

Gas Mixing ◽

Mixing Ratios ◽

Mass Fluxes ◽

Single Column ◽

Convective Mass Flux

Abstract Convection strongly influences the distribution of atmospheric trace gases. General circulation models (GCMs) use convective mass fluxes calculated by parameterizations to transport gases, but the results are difficult to compare with trace gas observations because of differences in scale. The high resolution of cloud-resolving models (CRMs) facilitates direct comparison with aircraft observations. Averaged over a sufficient area, CRM results yield a validated product directly comparable to output from a single global model grid column. This study presents comparisons of vertical profiles of convective mass flux and trace gas mixing ratios derived from CRM and single column model (SCM) simulations of storms observed during three field campaigns. In all three cases, SCM simulations underpredicted convective mass flux relative to CRM simulations. As a result, the SCM simulations produced lower trace gas mixing ratios in the upper troposphere in two of the three storms than did the CRM simulations. The impact of parameter sensitivity in the moist physics schemes employed in the SCM has also been examined. Statistical techniques identified the most significant parameters influencing convective transport. Convective mass fluxes are shown to be strongly dependent on chosen parameter values. Results show that altered parameter settings can substantially improve the comparison between SCM and CRM convective mass flux. Upper tropospheric trace gas mixing ratios were also improved in two storms. In the remaining storm, the SCM representation of CO2 was not improved because of differences in entrainment and detrainment levels in the CRM and SCM simulations.

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A Synergy Approach to Estimate Properties of Raindrop Size Distributions Using a Doppler Lidar and Cloud Radar

Journal of Atmospheric and Oceanic Technology ◽

10.1175/2010jtecha1377.1 ◽

2010 ◽

Vol 27 (6) ◽

pp. 1095-1100 ◽

Cited By ~ 5

Author(s):

Katja Träumner ◽

Jan Handwerker ◽

Andreas Wieser ◽

Jens Grenzhäuser

Keyword(s):

Size Distribution ◽

Analytical Description ◽

Doppler Lidar ◽

Fall Velocity ◽

Rayleigh Approximation ◽

Size Dependent ◽

Cloud Radar ◽

Raindrop Size Distribution ◽

Remote Sensing Systems ◽

Raindrop Size

Abstract Remote sensing systems like radars and lidars are frequently used in atmospheric measurement campaigns. Because of their different wavelengths, they operate in different scattering regimes. Combined use may result in new measurement options. Here, an approach to estimate raindrop size distribution using vertical velocities measured by a lidar–radar combination is introduced and tested using a 2-μm Doppler lidar and a 35.5-GHz cloud radar. The lidar spectra are evaluated to deduce air motion from the aerosol peak and the fall velocity of the raindrops from the rain peak. The latter is weighted by the area (D2) of the scatters. The fall velocity derived from radar measurements is weighted by D6 (Rayleigh approximation). Assuming a size-dependent fall velocity and an analytical description of the drop size distribution, its parameters are calculated from these data. Comparison of the raindrop size distribution from the lidar–radar combination with in situ measurements on the ground yields satisfying results.

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