Transcript Tollerud 3 June & 9 June LLJ Poster

Multi-scale Analyses of Moisture and Winds during the 3 and 9 June IHOP Low-Level Jet Cases
Edward Tollerud, Fernando Caracena, Adrian Marroquin, Brian Jamison*, and Steve Koch
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NOAA Forecast Systems Laboratory and Cooperative Institute for Research in the Environmental Science (CIRES)*
Two IHOP Morning Low Level Jet (LLJ) Missions
Description and Comparisons of LLJ Wind and Moisture Structure vis-à-vis Mission Science Objectives
On the mornings of June 3 and June 9, aircraft missions were flown in the IHOP domain to observe LLJ circulations and moisture
structure. The primary instrumentation included extra standard radiosonde launches, aircraft-launched dropsondes, and airborne lidar
wind and moisture measurements from the DLR Falcon and Learjet. Using data observed from these platforms it is possible to
describe the moisture structure and transport in the LLJ in unprecedented detail and at multiple scales. We describe the observations
made in these missions and the flight tracks designed to observe them. Some initial model results from a detailed MM5 run are also
discussed. Sections of dropsonde and lidar moisture and wind observations are shown. Finally, an application of detailed dropsonde
profiles to assessment of radiosonde processing accuracy are presented.
HRDL observations of windspeed normal to the Falcon flight track during the June 9 mission, combined with simultaneous DIAL measurements of specific
humidity, will provide highly-resolved estimates of transport by the LLJ. When compared with computations using dropsonde measurements at a larger scale
(roughly 60 km separation of observations) and with radiosonde observations made at even larger scales, the lidar flux computations can begin to address
questions about the utility of moisture measurements at these fine scales. Specifically, the presence of correlations of the windfields with the moisture fields at
scales below that resolved by the operational network of radiosondes and profilers may be determined. Model runs that incorporate research observations by
dropsondes will also be compared with existing runs that do not to get another assessment of the impact of mesoscale observations on forecasts of LLJ transport.
DIAL (onboard lidar, DLR Falcon)
observations of specific humidity.
Compare with dropsonde-observed
section below. Anomalous
rectangular regions near east end of
section suggest cloud
contamination.
Jet Core Dropsonde Profile, June 9
DLR Falcon Dropsonde Sections Along the Northern Leg of the June 9 Flight Track
LASE Data from DC-8
LLJ Mission Forecasting
Issues involved with forecasting LLJ occurrences for
IHOP mission planning are revealed in the two RUC
10 km 12h forecasts for 1200 UTC June 9 shown
above and to the right. A jet with good moisture that
met windspeed criterion was suggested in the surface
fields in central and western KS and OK. Secondly,
for optimum performance of the lidar sensors on the
Falcon, essentially cloud-free conditions were
required. The forecast of cloudtops (above) suggested
possible trouble, and indeed some slight cloud
contamination was encountered.
Windspeed (m/s). The core of the LLJ is
indicated near the eastern end of the
flight leg at a pressure of about 820 mb.
Terra Modis Satellite Image, 1641 UTC 3 June 2002
June 9 Aircraft Tracks and Dropsonde Observation Locations
Mixing Ratio (r) in g/kg. The depth of the
moist boundary layer increases
eastward. The mid-boundary layer
dryness at the extreme east end is
relected also in the DIAL sections above
Moisture Transport across the northern
side of the flight box as given by v . r,
where v is the wind component
transverse to the flight leg..
Radiosonde Processing and IHOP Observations
S-POL Radar Doppler Velocities
MODELING STUDY, JUNE 3 CASE
The RAMS model was initialized with LAPS analyses fields
for 1500 UTC 3 June 2002 over the IHOP area with lateral
boundary fields taken from the RUC20 model. For verification,
we use the NOWRAD patterns for 3 June 2002, valid at 1800
UTC shown below. The model was run in a two-nested grid
configuration with the innermost grid spacing of 4 km and an
external grid of 12 km. A horizontal cross section of wind
vectors, isotachs (red), and precipitation (black) from a 3-h
forecast is shown at the right. The initial fields are from LAPS
analysis with conventional data (no IHOP observations) and
include the "hot start" diabatic initialization procedures (which
includes moisture and consistent vertical velocities) to describe
Jet Core Dropsonde Profile
the initial cloud field. The wind barbs and isotachs
in the figure seem to suggest that the LLJ splits into
two branches (upper right of figure), with one
branch feeding the convective activity over Kansas
and the other continuing to the northeast (upper right
of figure). The precipitation pattern correlates with
the NOWRAD radar shown to the lower left.
The figure shows a comparison of two vertical wind
profiles (80 km Eta initial field, dashed and dropsonde
data, solid) taken at the first dropsonde release point on
1104 UTC 3 June 2002. The Eta wind profile was
obtained from the grid point nearest to the dropsonde
location, and includes the boundary layer level output
as well. Note that the boundary layer resolution of the
model is not manifest in the initial fields because the
model has been fed coarse, "minute" wind information
from the radiosondes.
NAST Lidar data Proteus aircraft
June 3 Aircraft Tracks and Dropsonde Observation Locations
NOWRAD radar mosaic valid 1800 UTC 3 June 2002. Notice the radar
pattern across New Mexico-Texas border, which suggests convective
activity forecasted by RAMS
Dropsonde data taken during Ihop has allowed us to
see the vertical structure of low-level jets that
developed over the area of the field experiment with a
vertical sample interval better than 5 m. The terminal
speeds of these dropsondes was about 7 m/s and the
wind sample rate was 0.5 s . Contrast these values with
those of radiosondes, which rise at 5 m/s and wind
samples are taken every 6 s . During IHOP, an archaic
procedure used by NWS in coding transmitted wind
data described by Doswell (http://www.cimms.ou.edu/
~doswell/NWSwinds/NWS_Winds.html), futher
degraded wind measurements, resulting in a
corresponding degradation of initial wind data in the
Eta model.
The coarser radiosonde wind data has resulted in a 1520 % maximum wind error in the wind speed at and
below the level of maximum winds. The effect is
magnified in the horizontal moisture transport, which
is computed from the product of the mixing ratio and
wind speed (profiles shown in bottom figure). The
sharp peak in vertical profile of moisture transport by
the LLJ is located at about 300 m above ground level
(AGL). Looking at the structure of the Eta wind
profile, one can see that there would be a large error in
moisture transport below 800 m AGL.