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A Preliminary Convective Climatology of Central United States Radiosonde Data

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A Preliminary Convective Climatology of Central United States Radiosonde Data ... There are nontrivial erroneous radiosonde data of all types, especially at the ... – PowerPoint PPT presentation

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Title: 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 lt 5 miles)
  • TFX, GTF (site moved lt 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 lt 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

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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

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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
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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…

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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!
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