A Preliminary Convective Climatology of Central United States Radiosonde Data

1. A Preliminary Convective Climatology of Central United States Radiosonde Data Matthew J. Bunkers, NWS UNR Presented at the 5th High Plains Conference 10/3/200110/5/2001

2. Objectives • Examine some of the similarities and differences between the convective environments of the northern High Plains (NHP) and the central/southern Plains (CSP) • Help discern what convective mode most commonly produces NHP severe convective wind events • Illustrate differences in certain convective parameters due to the choice of the lifted parcel, or the measure of vertical wind shear • Bring to light some of the limitations of the radiosonde database

3. Sounding Locations • Northern High Plains (NHP): • UNR, RAP (site moved ~10 miles) • BIS • GGW (site moved < 5 miles) • TFX, GTF (site moved < 5 miles) • Central/Southern Plains (CSP): • ILX, PIA, RAN (site moved ~40 miles) • SGF, UMN, COU (site moved ~125 miles) • TOP (site moved ~10 miles) • OUN, TIK, OKC (site moved ~15 miles) • LBF (site moved < 5 miles)

4. Radiosonde Data • NCDC & FSL databases from 1948-2000 • CDROM and online (hydrostatically checked) • Data processing applied: • Checks for lapse rates, bad surface data, missing data, spikes, and tolerance ranges • 611% of NHP (23% of CSP) soundings rejected because of these checks • Virtual temperature correction for CAPE (use Tv) • Soundings, that passed checks, used if: • SBCAPE  50 J kg-1 & SBCIN  50 J kg-1

10. Thermodynamic Summary • Positive SBCAPE is larger, and occurs more frequently, across the CSP vs. the NHP; but the SBCIN is larger on average • Precipitable water, especially in the lower atmosphere, is around 1.5 times higher over the CSP vs. the NHP • LCL heights are consistently lower across the CSP vs. the NHP

15. Kinematic Summary • The SRH supports relatively more right-moving supercells across the CSP (enhanced curvature); SRH values are nearly double over the CSP during the relative peaks in severe weather season • Hodographs are more unidirectional across the NHP vs. the CSP

16. NHP vs. CSP Parameters • Linear, or bulk, shear is similar between the NHP and CSP during their relative peak severe convective high wind seasons • Low-level moisture and CAPE are less and LCL heights are greater over the NHP vs. the CSP during their relative peak severe convective high wind seasons

17. ML

20. Parameter Summary • Considerable difference exists in SB vs. ML parcels, including derived parameters, such as BRN • A 500- or 1000-m ML parcel may be more useful than a SB parcel (e.g., Weisman and Klemp 1982; Bluestein and Jain 1985; Rasmussen and Blanchard 1998; Gilmore and Wicker 1998)

21. Parameter Summary Cont. • The total shear is often 23 times the bulk shear, so care should be taken when comparing shear between studies…

24. Radiosonde Summary • There are nontrivial erroneous radiosonde data of all types, especially at the surface (e.g., missing winds are common during the early record) • Several instrumentation changes have occurred over time/space, which can have significant impacts on observed trends of certain convective parameters…

25. New Surface Observations

26. The End!