Latent Heating and Cooling Rates in Developing and Nondeveloping Tropical Disturbances during TCS-08: TRMM PR versus ELDORA Retrievals*

Abstract

Unique sets of Electra Doppler Radar (ELDORA) observations in both developing and nondeveloping tropical disturbances in the western North Pacific are used to retrieve latent heating and cooling rates. During the reintensification of Sinlaku, maximum heating rates of about 80 K h 21 are diagnosed in the upper troposphere in the region of a strong updraft and maximum cooling rates of about 245 K h 21 are diagnosed in the lower troposphere in the region of a strong convective-scale downdraft. The southern convective burst in the pre-Nuri mission had a lower-tropospheric maximum in latent heating that was a more favorable condition for tropical cyclone formation than was the upper-tropospheric maximum in heating and the lowertropospheric maximum in cooling in the northern convective burst. Two nondeveloping tropical disturbances had deeper layers of more uniform heating and of cooling rates, and some evidence of more shallow cloud tops, that distinguished them from the developing cases. Although the Shige et al. Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) algorithm was only intended to be applied over large areas on longer time scales, the PR-derived latent heating profiles were compared with the ELDORA-derived profiles to reveal important mesoscale effects. Because all six cases indicated near-zero cooling rates, a new TRMM PR algorithm should be developed that would include the effects of saturated convective-scale downdrafts in tropical mesoscale convective systems (MCSs). Production of a legacy TRMM PR dataset with this improvement would be useful for diagnosing tropical cyclone formation dating back to 1998, and for specifying initial and validation conditions for numerical models in the tropics.

Observations of a Nondeveloping Tropical Disturbance in the Western North Pacific during TCS-08 (2008)

“…This increased the negative impact potential of downdrafts (i.e., increased DCAPE). Consistent with this assumption, Park and Elsberry (2013) concluded that evaporative cooling and strong downdrafts counteracted low-level spinup for TCS025 based upon an examination of latent heating and cooling rates retrieved from ELDORA radar during IOP-3. Molinari et al (2013) hypothesized that repeated lulls in convective activity for Tropical Storm (TS) Edouard (2002) were a result of vertical wind shear-induced ventilation that caused low-u e air to be transported into the boundary layer via downdrafts.…”

Tropical Cyclone Mekkhala’s (2008) Formation over the South China Sea: Mesoscale, Synoptic-Scale, and Large-Scale Contributions

“…Among the channels, polarized corrected temperature (PCT) at 85 GHz is used in this study since it responds to ice scattering in the deep convective towers. The TMI TBs at 85.5 GHz have effective fields of view of 7 km 3 5 km (Park et al 2007). …”

“…When the strong large-scale southwesterlies are present over the South China Sea owing to the eastward movement of the MJO over the western North Pacific (section 4), the primary area in which most of the MCSs and heavy precipitation originate is upstream and over the Philippines (Hoyos and Webster 2007;Ho et al 2008;Park et al 2011). Based on an analysis of eight years of TRMM PR rain rates, Ho et al (2008) found out that the diurnal maximum of rainfall during the WWB period occurs in the late morning.…”

“…6b-d), the MCS gradually dissipated as it moved westward toward the central South China Sea. The mechanism for the diurnal formation/decay of this offshore MCSs system was explained by Park et al (2011) as being due to two primary factors: (i) diurnally varying, large-scale westerlies that are associated with land surface heating of the Asian continent; and (ii) a local mesoscale diurnal circulation associated with the Philippines [see Fig. 11b of Park et al (2011)].…”

“…Such a TC formation poses a significant threat to heavily populated coastal regions. Predicting the timing and location of TC formation remains challenging (e.g., Nolan 2007;Fovell et al 2009;Lang et al 2012;Park et al 2013). The extent to which physical processes over adjacent land areas may contribute to TC formation over the South China Sea is an additional complication.…”