Observation report of MRR(3)

Tomoki Koshida

Research fellow of OKI/KANAE LAB

Introduction• Micro rain radar (MRR) are introduced in

IIS at late July 2003

Today’s topic

The difference of rain fall rate by MRR and by ground based rain gauge

1. Check the ground based

2. check the MRR algorism

From Previous talk

rr200mと地上雨量の比較

0

20

40

60

80

100

120

0 10 20 30 40 50 60

0.5mm mmバケツ雨量計雨量（ ）

mm/h

レーダ雨量（

）

Check the rain gauge

The result of check

0.5mm 雨量計の検定結果 y = 0.91 xR2 = 0.99

0

10

20

30

40

50

0 10 20 30 40 50 60

流入から見積もられる雨量

地上雨量計のイベントから算

出される雨量

Next check MRR algorism

• Observed the reflectivity by Doppler spectrum(observed speed)

• Doppler spectrum related to rain drop size

• The reflectivity related to the number of drops

Drop size & fall velocity

• Gunn & Kinzer(1949)

number distribution

粒径分布の比較

1.E-011.E+001.E+011.E+021.E+031.E+041.E+051.E+061.E+07

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

粒径

スペクトル密度

2.2mm/ h 22.4mm/ h 60mm/ h 110mm/ h

Contribution by drop size spectrum

粒径別の降水強度に対する寄与率

0.0

5.0

10.0

15.0

20.0

25.0

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

(mm)粒径

(mm

/h)

降水強度

2mm/ h 24mm/ h 60mm/ h 110mm/ h

The result of past research

• Best(1950)

conclusion

• Ground based rain gauge is right at the range 10mm/h to 50mm/h

• Smaller droplet observation of MRR is suspicious for quantitative observation