Aircraft Based Studies
Climatologically, the central part of Saudi Arabia receives its major rainfall between November and March. The rainfall is highly variable, however. A field program will occur between 1 November 2006 and 30 March 2007. The objective will be to document the microphysics and dynamics of both natural and seeded clouds using two aircraft instrumented for air chemistry and cloud physics measurements: a Piper Cheyenne II and a Learjet. In addition, two seeding aircraft (Piper Cheyenne II) will be employed along with the weather radars. The aerosol and cloud physics aircraft will collect data in the target clouds both prior to and following cloud seeding; these research aircraft will also be used for seeding The goal is to maximize the opportunities to collect airborne data in clouds, allowing for sufficient information from cloud survey flights and seeding trials. The emphasis will be to evaluate and assess if and what potential exists to enhance rainfall via cloud seeding by conducting measurements and seeding flights. During periods of clear skies, air chemistry surveys and case studies of plume behavior will be conducted to assess local sources of aerosols and pollution that could have an effect on cloud and rainfall processes.
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|
Cheyenne II with standard instrumentation |
Learjet |
Aircraft Instrumentation
For adequate sampling of particles in and around clouds, the research aircraft
has the capability of measuring the size distribution of particles in the
temporarily suspended aerosol range and in the cloud hydrometeor range. The
following table indicates the standard suite of instrumentation on each research
aircraft. Additional instrumentation will be deployed on the Learjet, including:
TAMU Differential Mobility Analyzer (DMA) for properties of aerosol sized
0.01µm to 0.5µm, DMT CAPS and LWC probes to measure cloud properties
between 2 to 1600µm, and the SPEC, Inc. HVPS probe to image particles
between 0.025 and 6 mm. Additional aerosol measurements will be made using
the Learjet and include: submicron size distribution (DMA), CCN concentration
(DMT CCN), and IN concentration.
TABLE 1: Basic instrument package for the WMI Cheyenne and Learjet research aircrafts
|
Variable |
Instrument |
Range |
Accuracy |
Resolution |
Frequency |
|
Air temperature |
Rosemount 102DB1CB |
-50°C to +50°C |
0.1°C |
0.01°C |
1 Hz |
|
Air temperature |
0.038" DIA. |
-30°C to +50°C |
0.05°C/0.3°C incl DHC |
0.01°C |
< 1 s TC |
|
Relative humidity (reverse flow) |
ThermosetPolymer RH Sensor |
0 to 100% RH |
2% RH |
0.1% RH |
5 s TC @ 20°C |
|
Barometric pressure |
MEMS Pressure Sensor |
0 to 110000 Pa |
100 Pa |
10 Pa |
20 Hz |
|
u wind component |
Extended Kalman Filter (EKF) |
0.50 m/s @ 75 m/s TAS |
0.01 m/s |
5 Hz |
|
|
v wind component |
Extended Kalman Filter (EKF) |
0.50 m/s @ 75 m/s TAS |
0.01 m/s |
5 Hz |
|
|
w wind component |
Extended Kalman Filter (EKF) |
0.50 m/s @ 75 m/s TAS |
0.01 m/s |
5 Hz |
|
|
Position (Latitude/Longitude) |
WAAS DGPS |
2 m (2 ) |
< 1 m |
5 Hz |
|
|
Altitude |
WAAS DGPS |
-300 to 18000 m |
5 m (2 ) |
< 1 m |
5 Hz |
|
Geometric Altitude |
King KRA 405 Radar Altimeter |
0 to 2000 ft |
3% < 500 ft 5% > 500 ft |
0.48 ft (0.15 m) |
|
|
Pitch Attitude (o) |
MEMS IMU/GPS/EKF |
-60 to +60° |
0.2° |
0.01° |
5 Hz |
|
Yaw Attitude (o)/ Heading |
MEMS IMU/GPS/EKF |
0 to 360° |
0.1° |
0.01° |
5 Hz |
|
Angle of attack (o) |
MEMS Pressure Sensor |
-15 to +15° |
0.03° @ 150 m/s |
0.001° @ 150 m/s |
20 Hz |
|
Side-slip (o) |
MEMS Pressure Sensor |
-15 to +15° |
0.03° @ 150 m/s |
0.001° @ 150 m/s |
20 Hz |
|
True Air Speed |
MEMS Pressure Sensor |
0 to 150 m/s |
0.1 m/s |
0.01 m/s |
20 Hz |
|
Video record |
Sony DCR-DVD 201 |
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|
Logging, telemetry & event markers |
ESD DTS (GPS) |
1 Hz |
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|
Cloud droplet spectra |
DMT SPP |
2 to 50 µm |
1 to 2 µm, 30 bins |
1 Hz |
|
|
Liquid water content |
DMT LWC-100 |
0 to 3 g/m3 |
0.05 g/m3 |
0.01 g/m3 |
1 Hz |
|
Liquid water content |
SPP calculated |
> 3 g/m3 |
1 Hz |
||
|
Isokineticaerosol inlet |
Brechteldouble diffuser inlet |
28 lpm |
100 m/s |
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|
CCN |
DMT CCN counter |
0.5 to 10 µm 0.1 to 1.2 % SS |
see text |
0.5 µm, 20 bins |
1 Hz |
|
Aerosols |
PMI PCASP |
0.1 to 3μm |
15 bins |
1 Hz |