IR-only Tropical Cloud Regimes Data Product

Introduction

Distinctive mesoscale distributions of cloud top pressure and optical thickness have been identified in the tropics and shown to indicate different states of the atmosphere, particularly distinguishing between deep-convectively-active and suppressed conditions (Jakob and Tselioudis 2003, Rossow et al. 2005). However, since these cloud regimes were limited to daytime conditions because cloud optical thickness was determined from reflected sunlight, the effective time sampling scale is one day.


Tan and Jakob (2013) have extended this analysis by compositing the profiles of cloud top pressure that are associated with the daytime cloud regimes so as to resolve diurnal variations of the cloud regimes. Although some regimes involving low-level cloudiness of different optical thicknesses are not separated, the main types of deep-convectively-active and suppressed conditions are still identified. The data product provides a classification of each 2.5 degree grid cell every three hours over the whole extended tropical zone (± 35° latitude) for the period of August 1983 through June 2008. The shape of the cloud top pressure profile patterns that define each of the eight regimes is shown in the figure below.


IR-only Cloud Regimes Regime Vertical RFO
ISCCP Map

The data is recorded in NetCDF format.

To download the dataset (IRregimes.tgz), click HERE.

To download the cluster centroid (ir_centroids.txt), click HERE.


More information, as well as the data, are available at the Monash University Climate and Weather group.


References

  • Tan, J., and C. Jakob (2013), A three-hourly data set of the tropical convection based on cloud regimes, Geophys. Res. Lett., 40, 1415-1419, DOI 10.1002/grl.50294.
  • Jakob, C., and G. Tselioudis (2003), Objective identification of cloud regimes in the Tropical Western Pacific, Geophys. Res. Lett., 30, 1-4, DOI 10.1029/2003GL018367.
  • Rossow, W.B., Tselioudis, G., Polak, A., and Jakob, C (2005), Tropical Climate Described as a Distribution of Weather States Indicated by Distinct Mesoscale Cloud Property Mixtures, Geophys. Res. Lett., 32.