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OLR-Dec2014-Jan2015-24hrAVG - Ralph Milliff

Out-going longwave radiation (OLR) anomalies (Wm-2) from the OLR-SYN dataset are shown for the tropical Indian and western Pacific regions (23.5í N to 23.5íS, 40íE to the dateline).  The period 10 December 2014 to 15 January 2015 spans an active phase for the Madden-Julian Oscillation (MJO) in the domain.  OLR anomalies are computed by removing a 24 hr running mean.  OLR-SYN data are available at 1í resolution every 3 hours. Deep blues correspond to the deepest convective cloud tops inhibiting the most OLR.  Oranges and reds correspond to surface or very shallow clouds exhibiting little or no OLR inhibition.  Clusters of deep and lighter blues coalesce and propagate slowly eastward in irregular fits and starts.  The average eastward propagation speeds are O(15 ms-1).  Rossby gyre circulations are evident in several instances in each hemisphere in the lee of the eastward propagating supercluster of deep convection.  This is consistent with the classic linear theory due (separately) to Matsuno and Gill (e.g., the Matsuno-Gill model).  

Surface Rain Rate - Ralph Milliff

Surface rain rate (mm hr-1) from the Global Precipitation Mission (GPM) Integrated Multi-Satellite Retrievals for GPM (IMERG) product, at half-hourly and 9 km resolutions.  The domain spans the tropical Indian and western Pacific regions (23.5°N to 23.5°S, 40°E to the dateline) for the period 10 December 2014 through 15 January 2015.  This period corresponds to an active phase for the Madden-Julian Oscillation (MJO) in the domain.  Coherent patches of surface rain rate indicate mature mesoscale convective systems (MCS).  The MCS life cycles span a few hours to a few days.  Westward propagation in the MCS is most common but MCS can also be advected in all directions.  What is less evident is the aggregation of the MCS and the slow, irregular eastward propagation of successive ensembles of MCS over the length of the period shown here.

OLR Dec2014 Jan2015 24hrAVGwithGPM- Ralph Milliff

Surface rain rate from the Global Precipitation Mission (GPM) IMERG product that estimates surface rain rate from infrared and microwave radiometer retrievals from up to 9 different international satellites (i.e., the GPM constellation).  Surface rain rate (mm hr-1) is available at 9 km resolution, every half hour.  A semi-transparent field of coincident out-going longwave radiation (OLR) anomaly from the OLR-SYN dataset overlies the surface rain rate from GPM IMERG.  See the OLR-only animation for details of that dataset.  Again, the domain is the tropical Indian and western Pacific ocean region and the period of interest spans an MJO active phase from 10 December 2014 through 15 January 2015.  Surface rain rate patches correspond to mature Mesoscale Convective Systems (MCS) in the domain.   Individual MCS interact and form regional ensembles affecting a continuous OLR signal in a so-called supercluster entity.  For the most part, the MCS are seen to propagate westward with life-cycles that span up to a few days.  This contrasts with the slow and irregular eastward propagation of the supercluster indicated in the OLR.

MJO GPM with SCAT Div 2000- Ralph Milliff

Surface rain rate (mm hr-1) from GPM IMERG with intermittent coverage of surface wind divergence (s-1) from RapidSCAT and ASCAT scatterometers.  The same tropical Indian and western Pacific domain and MJO active phase (10 December 2014 – 15 January 2015) is captured (see also OLR only and OLR plus GPM IMERG animations).  Broadswath divergence retrievals are from the RapidSCAT instrument aboard the International Space Station.  RapidSCAT surface vector winds are retrieved at 12.5 km resolution.  Twin, narrow-swath retrievals are from the ASCAT instrument on Metop-A.  ASCAT surface vector wind retrievals are at 25 km resolution.  Surface divergence is computed via a boundary integral method (i.e., using the Divergence Theorem).  Boundary circuit diameters are only 2 wind vector cells wide and the rain impact advice from the RapidSCAT data are ignored.  Surface wind convergence lines occur at leading edges of mature, propagating mesoscale convective systems (MCS) indicated by coherent patches in the surface rain rate. Less obvious, broader-scale divergence patches are sometimes evident to the lee of the convergence lines.  These external properties of the MCS are consistent with MCS descriptions.   The animation can be stopped and stepped forward using arrow keys for several frames so as to better view the signals in intermittent scatterometer coverage.  Only a small subset of the MCS in the domain are sampled by the scatterometers at any time.

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