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Column Introduction This page describes two studies of different convective cases; one over N. America associated with formation of severe tornadoes, the other over central Africa. Both cases are studied starting the forecast from the same date/time (initial conditions). The N.America case has strong large scale forcing whereas the central African case is driven by the diurnal cycle. US Tornado convection case (Arkansas) On the 27 April 7pm local time (00UTC 28 April), tornadoes hit towns north and west of Little Rock, Arkansas killing approx 17 people.  (http://edition.cnn.com/2014/04/28/us/severe-weather/index.html?hpt=hp_c2). On the evening on the 28 April fatal tornadoes occurred over Mississippi (http://www.bbc.co.uk/news/world-us-canada-27199071). More information can also be found on the ECMWF Severe Event Catalogue 201404 - Convection - Arkansas U.S. African diurnal deep convection (Central Africa)  To be done. Column Panel borderColor white bgColor white titleBGColor white Panel bgColor white titleBGColor #dcf0f7 borderStyle dotted title On this page... Table of Contents maxLevel 3 indent 10px

Initial conditions

 To be done.

Key questions to address with the control forecast

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• Increase the precipitation auto conversion rate - what impact does this have?

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  title How to change the code (click here to expand…)
  Edit the source code to increase the auto conversion rate by 20% File: ifs/phys_ec/sucldp.F90, change: Code Block line 123: RKCONV=1._JPRB/6000._JPRB ! 1/autoconversion time scale (s) to: Code Block line 123: ! RKCONV=1._JPRB/6000._JPRB ! 1/autoconversion time scale (s) line 124: RKCONV=1.2_JPRB/6000._JPRB ! default scaled by 20%: 1/autoconversion time scale (s)

• Impact of the improved diurnal cycle of convection. The improved diurnal cycle can be switched on and off in the model using the model namelists.
  In this sensitivity experiment, look at the timing of convective and precipitation events.

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  title How to change the representation of diurnal convection (click here to expand...)
  Namelist block NAMCUMF, parameter RCAPDCYCL RCAPDCYCL = 2 (default) activates the diurnal cycle using sub-cloud CAPE, RCAPDCYCL = 1 diurnal cycle using surface sensible heat flux, RCAPDCYCL = 0 reverts the code to a setting before the diurnal cycle for convection was implemented

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Optimization factor for the time scale adjustment:

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