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| Name | Last modified | Size | Description |
|---|---|---|---|---|
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| sgpcape.199301.cdf | 2014-09-18 18:00 | 22K | |
| sgpcape.199401.cdf | 2014-09-18 18:00 | 186K | |
| sgpcape.199501.cdf | 2014-09-18 18:00 | 199K | |
| sgpcape.199601.cdf | 2014-09-18 18:00 | 200K | |
| sgpcape.199701.cdf | 2014-09-18 18:00 | 193K | |
| sgpcape.199801.cdf | 2014-09-18 18:00 | 130K | |
| sgpcape.199901.cdf | 2014-09-18 18:00 | 159K | |
| sgpcape.200001.cdf | 2014-09-18 18:00 | 169K | |
| sgpcape.200101.cdf | 2014-09-18 18:00 | 172K | |
| sgpcape.200201.cdf | 2014-09-18 18:00 | 192K | |
| sgpcape.200301.cdf | 2014-09-18 18:00 | 173K | |
| sgpcape.200401.cdf | 2014-09-18 18:00 | 181K | |
| sgpcape.200501.cdf | 2014-09-18 18:00 | 178K | |
| sgpcape.200601.cdf | 2014-09-18 18:00 | 177K | |
| sgpcape.200701.cdf | 2014-09-18 18:00 | 175K | |
| sgpcape.200801.cdf | 2014-09-18 18:00 | 173K | |
| sgpcape.200901.cdf | 2014-09-18 18:00 | 174K | |
| sgpcape.201001.cdf | 2014-09-18 18:00 | 176K | |
| sgpcape.201101.cdf | 2014-09-18 18:00 | 183K | |
| sgpcape.201201.cdf | 2014-09-18 18:00 | 179K | |
ARM soundings are used to determine Convective Available Potential Energy (CAPE), Convective Inhibition (CIN) and associated properties, using the following relationships:
Where, EL is the equilibrium level, LFC is the level of free convection, TPv is the virtual temperature of a rising parcel, TEv is the virtual temperature of the environment, g is the acceleration due to gravity and ∆Z is the height increment.
The convective parcel characteristics are determined by raising a parcel from the surface (see definition of surface parcel characteristics) dry adiabatically until it reaches the lifting condensation level (LCL). The parcel then ascends moist adiabatically from the LCL through the level of free convection (LFC) until it reaches the equilibrium level. Important details regarding the determination of the properties of the rising convective parcel are:
The CAPE PI product contains calculations for two types of CAPE based upon selection criteria of the surface (Sfc). The first, cape_type=0, is a maximized CAPE for which the level from which to raise the parcel is determined by locating the level of the maximum virtual environmental temperature within the first kilometer. The second, cape_type=1, uses the first level of the sounding as the surface.
The equilibrium level (EL) is determined by locating the maximum height in the profile at which TEv and TPv cross.
The lifting condensation level (LCL) is found by first calculating the following profile of the temperature of the LCL (TLCL), where TE is the environmental temperature profile in K, and Td is the environmental dewpoint temperature profile in K (Bolton, 1980):
The level at which the resultant profile's temperature at the Sfc is equal to the temperature along the dry adiabat is the LCL.
The profile of the dry adiabat is calculated as follows, where Z is the height profile in meters AGL, ZSfc is the Sfc height in meters AGL, and TSfc is the temperature in K at the Sfc:
The level of free convection (LFC) is determined by locating the height at which TPv becomes definitively greater than TEv. First, possible LFCs are located at points above the surface where TPv - TEv equals 0 or changes from negative to positive. In addition, the sum of the differences (TPv - TEv), for the subsequent 15 time/pressure steps must be positive. If one possible LFC is found, then it is used as the LFC. If no LFC is found, then the LFC is set to -9999. If more than one possible LFC is found, then the level, between the surface and the EL, at which the difference between TPv and TEv is greatest, and TEv is greater than TPv, this level is identified. The possible LFC above this point is chosen as the LFC.
The mixed layer height is determined by sub-sampling the profile to 5 Mb levels, calculating the environmental potential temperature lapse rate (∆θ/∆Z), and then smoothing to 15 Mb averaged layers. The level at which ∆θ/∆Z is first >= 0.005 K m-1 is identified as the bottom of an inversion layer (L1). The level, above that, at which ∆θ/∆Z dips below .005 K m-1 is identified as the top of the layer. If the potential temperature at any point within the layer is greater by at least 2 K from that of L1, then the height of the mixed layer has been identified at the level of that point (Marsik et al., 1995). If the potential temperature delta criterion is not met, then the profile is scanned for another inversion layer, up to 5 layers in all, until a mixed layer height is found. In some cases, the potential temperature delta criterion is not met in any layer and no mixed layer height can be reported. Please note that the mixed layer height provided in this PI product should match the PBL Sonde VAP PBL height for the Heffter method (Hefter, 1980), except in cases for which the PBL Sonde VAP considers the level to be indeterminate. In these cases, the CAPE/CIN product will be -9999, even though the PBL Sonde VAP will attempt a value, reflecting the indeterminate status in its QC.
Bolton, D., 1980: The computation of equivalent potential temperature. Mon. Wea. Rev., 108, 1046–1053.
Heffter JL. 1980. “Transport Layer Depth Calculations.” Second Joint Conference on Applications of Air Pollution Meteorology, New Orleans, Louisiana.
Marsik FJ, KW Fischer, TD McDonald, and PJ Samson. 1995. “Comparison of Methods for Estimating Mixing Height Used During the 1992 Atlanta Field Intensive." Journal of Applied Meteorology 34(8):1802–1814.
To cite the data, please use the data DOI 10.5439/1127238 or http://dx.doi.org/10.5439/1127238
Suggested Citation Structure
Example for SGP.C1 site data:
Mike Jensen. 2013, updated yearly. ARM Convective Available Potential Energy (CAPE), Convective Inhibition (CIN) Product from ESM FASTER project. Jan 1996-Jan 2011, 36° 6' 18.0" N, 97° 9' 6.0" W: Southern Great Plains Central Facility (C1). Oak Ridge, Tennessee, USA: Atmospheric Radiation Measurement (ARM) Climate Research Facility Data Archive. Data set accessed 2012-10-01 at http://dx.doi.org/10.5439/1127238.
See also DOI Guidance for ARM Facility Datastreams
Mike Jensen: mjensen@bnl.gov