On the cumulus diurnal cycle over the tropical warm pool

Abstract. The presence of clouds above the tropopause over tropical convection centers has so far been documented by spaceborne instruments that are either sun-synchronous or insensitive to thin cloud layers. Here we document, for the first time through direct observation by spaceborne lidar, how the tropical cloud fraction evolves above the tropopause throughout the day. After confirming previous studies that found such clouds most frequently above convection centers, we show that stratospheric clouds and their vertical extent above the tropopause follow a diurnal rhythm linked to convective activity. The diurnal cycle of the stratospheric clouds displays two maxima: one in the early night (19:00–20:00 LT) and a later one (00:00–01:00 LT). Stratospheric clouds extend up to 0.5–1 km above the tropopause during nighttime, when they are the most frequent. The frequency and the vertical extent of stratospheric clouds is very limited during daytime, and when present they are found very close to the tropopause. Results are similar over the major convection centers (Africa, South America and the Warm Pool), with more clouds above land in DJF (December–January–February) and less above the ocean and in JJA (June–July–August).

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Greatly Expanded Tropical Warm Pool and Weakened Hadley Circulation in the Early Pliocene

Science ◽

10.1126/science.1167625 ◽

2009 ◽

Vol 323 (5922) ◽

pp. 1714-1718 ◽

Cited By ~ 188

Author(s):

C. M. Brierley ◽

A. V. Fedorov ◽

Z. Liu ◽

T. D. Herbert ◽

K. T. Lawrence ◽

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Keyword(s):

Hadley Circulation ◽

Warm Pool ◽

Early Pliocene ◽

Tropical Warm Pool

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Testing ice microphysics parameterizations in the NCAR Community Atmospheric Model Version 3 using Tropical Warm Pool–International Cloud Experiment data

Journal of Geophysical Research Atmospheres ◽

10.1029/2008jd011220 ◽

2009 ◽

Vol 114 (D14) ◽

Cited By ~ 7

Author(s):

Weiguo Wang ◽

Xiaohong Liu ◽

Shaocheng Xie ◽

Jim Boyle ◽

Sally A. McFarlane

Keyword(s):

Atmospheric Model ◽

Warm Pool ◽

Experiment Data ◽

Tropical Warm Pool ◽

Model Version ◽

Ice Microphysics

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Impact of the Diurnal Cycle of Solar Radiation on Intraseasonal SST Variability in the Western Equatorial Pacific

Journal of Climate ◽

10.1175/jcli3432.1 ◽

2005 ◽

Vol 18 (14) ◽

pp. 2628-2636 ◽

Cited By ~ 71

Author(s):

Toshiaki Shinoda

Keyword(s):

Solar Radiation ◽

Mixed Layer ◽

Diurnal Cycle ◽

Intraseasonal Oscillation ◽

Warm Pool ◽

Surface Fluxes ◽

Surface Cooling ◽

Mixing Processes ◽

Surface Warming ◽

Sst Variability

Abstract The mechanism by which the diurnal cycle of solar radiation modulates intraseasonal SST variability in the western Pacific warm pool is investigated using a one-dimensional mixed layer model. SSTs in the model experiments forced with hourly surface fluxes during the calm–sunny phase of intraseasonal oscillation are significantly warmer than those with daily mean surface fluxes. The difference in two experiments is explained by upper-ocean mixing processes during nighttime. Surface warming during daytime creates a shallow diurnal warm layer near the surface (0–3 m), which can be easily eroded by surface cooling during nighttime. Further cooling, however, requires a substantial amount of energy because deeper waters need to be entrained into the mixed layer. Since the shallow diurnal layer is not formed in the experiment with daily mean surface fluxes, the SST for the hourly forcing case is warmer most of the time due to the diurnally varying solar radiation. Sensitivity of the intraseasonal SST variation to the penetrative component of solar radiation is examined, showing that the diurnal cycle plays an important role in the sensitivity. Solar radiation absorbed in the upper few meters significantly influences intraseasonal SST variations through changes in amplitude of diurnal SST variation.

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