The new Mountain Observatory of the Project “Optimizing Cloud Seeding
by Advanced Remote Sensing and Land Cover Modification (OCAL)” in the
United Arab Emirates: First results on Convection Initiation
Abstract
In this study, we discuss a new mountain peak observatory in the United
Arab Emirates (UAE). Using coordinated scan patterns, a Doppler lidar
and cloud radar were employed to study seedable convective clouds, and
identify pre-convection initiation (CI) clear-air signatures. The
instruments were employed for approximately two years in an extreme
environment with a high vantage point for observing valley wind flows
and convective cells. The instruments were configured to run
synchronized polar (PPI) scans at 0°, 5°, and 45° elevation angles and
vertical cross-section (RHI) scans at 0°, 30°, 60, 90°, 120°, and 150°
azimuth angles. Using this output 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 selected two cases in
unstable conditions - the 5 and 6 September 2018. In both cases, we
observed areas of convergence/divergence, particularly associated with
wind flow around a peak 2 km to the south-west. The extension of these
deformations were visible in the atmosphere as high as 3 km above sea
level. Subsequently, we observed convective cells developing in the same
directions – apparently connected with 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 demonstrate the value of synergetic
observations for understanding convection initiation, improvement of
forecast models, and cloud seeding guidance.