Graphical Abstract

• Tweet

Ciesielski, P. E., R. H. Johnson, K. Yoneyama, and R. K. Taft, 2014: Mitigation of Sri Lanka Island effects in Colombo sounding data and its impact on DYNAMO analyses. J. Meteor. Soc. Japan, 92, 385-405.
https://doi.org/10.2151/jmsj.2014-407

• Graphical Abstract with highlights
• Original PDF

Highlights:

• During the Dynamics of the MJO (DYNAMO) field campaign in 2011, 258 upper-air soundings were launched at Colombo, Sri Lanka as part of the enhanced northern sounding array (NSA) of the experiment. These soundings were affected at low levels by the diurnal heating of this large island and by flow blocking due to elevated terrain (> 2 km) to the east of the Colombo site. Because of the large spacing between sounding sites, these small-scale island effects are aliased onto the larger scale impacting analyses and atmospheric budgets over the DYNAMO NSA.
• To mitigate these local island effects on the large-scale budgets, a procedure was designed which used low-level ECMWF-analyzed fields in the vicinity of Sri Lanka (i.e., a 2.5° sampling radius from center of topographic feature seen in Fig. 2) to estimate open-ocean conditions at Colombo’s location as if the island were not present. These “unperturbed” ECMWF fields at low-levels were then merged with the observed Colombo soundings below 700 hPa.
• Results indicate a beneficial impact of using these adjusted fields on several aspects of the budget analyses (e.g., higher temporal correlations of budget-derived rainfall to independent estimates, elimination of negative budget rainfall during build-up phase of November MJO event, etc.).