Heated Condensation Framework

Assesses the atmospheric background state with respect to convective initiation using hBCL and θBM. Convection can also be identified as having been triggered due to local surface forcing when θdef equals zero. Additionally the amount of surface sensible heat flux necessary for triggering convection assuming no additional moisture inputs is defined by SHdef, representing the strictly heat pathway. Conversely the moisture pathway for triggering is quantified by LHdef and the most energy advantageous pathway is defined by Eadv. Finally the potential temperature, height above ground, and pressure at which a transition from heat to moisture advantage occurs is also returned by θtran, htran, and Ptran respectively.

Identifies which convective events originated due to local surface forcing. When θdef = 0 then the convection is identified as being triggered locally, otherwise the event was triggered by other non-local sources. When applying this distinction to model output be mindful of horizontal resolution because coarser resolutions would likely not capture the necessary surface heterogeneity. Generally grid sizes finer enough to resolve the dominate land surface type is sufficient, but the finer the better. See Figure Figures 2 and 7 from Part I, and Figures 5-8 from Part II

Quantifies that atmospheric background state by the variable θBM and hBCL. Higher θBM and hBCL translate to drier, more stable atmospheric background state with respect to convection. Practically these variables put the local surface forcing within the context of the background state. See Figure 7 from Part I, and Figure 1 from Part 2<

Helps assess whether the moisture or surface heating pathway is most efficient for triggering convection as quantified by Eadv. When Eadv is greater than 45, injecting moisture into the boundary layer through either evaporation or advection is more effective at triggering convection. When Eadv less than 45 means heating the surface is more efficient at triggering convection than injecting moisture. See Figures 5 and 6 from Part I, and Figure 9 from Part II.

Use morning measurements of the atmospheric background state, θBM, and collocated soil moisture to identify the states that are most conducive to triggering convection later in the day. This is a method for identifying positive and negative feedbacks between soil moisture and convection. See Figure 11 from Part II.

The above usages can be calculated from observations and models and then used to explore biases in convective initiation timing, atmospheric background state of convective triggering, the most energy efficient pathways for triggering, and local soil moisture-convection interactions.

Required Input Data:

Needs vertical profiles of temperature, specific humidity, pressure, and height. Works well with radiosonde data and model/reanalysis output.

temperature

specific humidity

geopotential height

pressure

Assess the atmospheric background state with respect to convective initiation and identifies local versus non-locally triggered moist convection.

Prototype Subroutine Call

subroutine hcfcalc ( nlev1 , missing, tmp_in, press_in, qhum_in, hgt_in, &
t2m , psfc , q2m , h2m , &
TBM , BCLH , BCLP , TDEF , &
TRAN_H , TRAN_P , TRAN_T, &
SHDEF_M, LHDEF_M, EADV_M )

Required Input

Output

Optional Output

How to Calculate

1
Increase the surface temperature (ideally 2 meter temperature) by some small increment.
2
Lift dry adiabatically locating where the incremented temperature intersects the observed temperature profile.
3
Mix the water vapor profile from the level of intersection to the surface.
4
Repeat until saturation occurs at the top of the level of intersection.

Relevant Citations

Method Description 

Tawfik, A.B., and P.A. Dirmeyer (2014), A process-based framework for quantifying the atmospheric preconditioning of surface-triggered convection, Geophys. Res. Lett., 41, doi:10.1002/2013GL057984

Tawfik, A., P.A. Dirmeyer, J.A. Santanello Jr. (2015), The Heated Condensation Framework. Part I: Description and Southern Great Plains Case Study, Journal of Hydromet. doi:10.1175/JHM-D-14-0117.1

  Detailed Evaluation 

Tawfik, A., P.A. Dirmeyer, J.A. Santanello Jr. (2015), The Heated Condensation Framework. Part II:  Climatological behavior of convective initiation and land-atmosphere coupling over the Continental United States, Journal of Hydromet. doi:10.1175/JHM-D-14-0118.1