Mobile Integrated Profiling System (MIPS) Observations of Boundary Layer and Water

Vapor Variations around Boundaries and Storms

Kevin KnuppUniversity of Alabama in Huntsville

IHOP_2002 Spring Science Workshop3/24/03-3/26/03

MIPS - Mobile Integrated Profiling System

MicrowaveProfiling

Radiometer

Dopplersodar

915 MHz Doppler Profiler

Lidar ceilometer

Surfaceinstrumentatio

n

18 June 2002Deployment 3

IRradiometer

Analysis activities at UAH• Examination of the characteristics of all boundaries that

passed over the MIPS (Ph.D. student) - see poster• 15 June case study (M.S. student, this presentation)• Heat burst event on 20 June around 0200-0230 Z (Knupp)

– very dry air within the heat burst (T 35 °C, Td 0 °C)– combination of multiple microbursts and vortices– Highly variable wind, peak gust to 33 m s-1, near encounter

with a vortex• Examination of a boundary layer entrainment event on 19

June; observed at the end of the CI experiment• Examination of the performance of the microwave profiling

radiometer (entire research team)– focus on the BLE days

15 June 2002 case summary• 15 June 2002, 1900-2400 UTC• Observations of a complicated, diffuse boundary

with small thermodynamic contrast. Three deployments were made around this boundary.

• Continuous observations were acquired as the eastward-moving boundary intersected the inflow zone of an existing intense thunderstorm– the boundary assumed a much better definition– enhanced inflow into the storm (blowing dust) was

observed– a strong gust front and outflow occurred 30 min later

Data presentation - 15 June case• 915 MHz Profiler (z = 60 m, t = 30-60 s)

– Vh, W, SNR (Z and Cn2), Doppler spectra, Tv(z)

• 0.905 m lidar ceilometer– cloud base & precip. properties (extinction), aerosols

• Microwave Profiling Radiometer (to 10 km)– T(z), v(z), PW, ILW, cloud base T (t = 14 min)

• Surface instrumentation (1 Hz)– T, RH, p, wind, solar radiation

• S-Pol Z• GOES-11 visible images

GOES 11 overview

1934 2003

Good definition in cloud field

2034 2103

Poor definition in cloud field

22032134

Anvil moves over the boundary

23342255

Intense storm with gust front over MIPS

1 2 3

3 deployments (surface data)

T, Td

Windspeed

Winddirection

Solarradiation

Anvil overhead

boundary

0

5

10

15

20

25

30

35

40

45

Radiometer values of PW and ILW (note time breaks)

1 2 3mm

Systematic increaseSystematic decrease

Profile

Deployments 1 and 2

Dep 1: Primarily west of boundary

Dep 2: Boundary passage - wind direction change

Lack of thermodynamic contrast in both cases

More significant clouds during boundary passage at 2055 UTC

1 2

boundary

+

MIPS

Deployment 1

+MIPS

Deployment 2

Winds from one set of 3 beams, plotted every 5 min

Red arrows indicate boundary location

Deployment 1 Deployment 2915 MHz profiler

Updraft with bndy at 1910? (deployment 1)

Enhanced SNR during bndy passage near 2050

Appears to be a difference in CBL properties for 1 and 2 (all moments)

SNR

W

V

Ceilometer: Cu cloud base near 1.8-2.0 km, some variation in backscatter at low levels associated with boundary passage

clouds clouds

Cloud base decrease following boundary passage

1 2

Radiometer T, v profiles at 1933

1000

700

5001922 1921west east

west east

d

Deployment 3Boundary passage near 2205 UTC? Oscillation? Intense vortex observed 2 km to the west.

Anvil passage overhead rapidly reduced surface heating. As a result, the CBL turbulence weakened.

Enhanced inflow into the approaching storm

Gust front passage at 2256 UTC. 2 mb pressure rise prior to arrival

T, Td

Wind speed

Wind direction

pressure

solar Gust front

boundary?

+MIPSMIPS

+MIPS

+MIPS

+MIPS

Deployment 3

Reduction in CBL turbulence due to cessation of surface heating.

Updraft activity near 2240 UTC

Acceleration of flow into the storm

Gust front passage at 2256 UTC - max updraft > 10 m s-1 and peak gust to 28 m s-1

T, v profiles at 2246: disappearance of the stable layer

2137 2220 (same location)

1000

700

500

Deeper layer of water vapor within the boundary zone; 35% increase in integrated vapor

Summary & future work• Subtle variations in ABL properties were measured across

the diffuse boundary.• A strong cap existed near 2 km AGL initially.• The cap eroded within the “sharpened” boundary zone near

an approaching storm. Low-level water vapor increased significantly within the boundary zone.

• The (main?) boundary appeared to contract as the storm approached, following a rapid reduction in solar heating. The storm intensified in the region where it intersected the boundary. What were the physical mechanisms?

• Future: comprehensive case study; combine sensors to retrieve more detailed T and v profiles.

End

Information on MIPS, with a (future) link to IHOP analysis efforts is at the following site:

http://vortex.nsstc.uah.edu/mips

915 MHz SNR - varied examples, 2/16/01

Ceilometer backscatter: cloud structure, precipitation properties, BL structure

MIPS measurements of a boundary (dry line) during IHOP