Exercise: Satellite Imagery Analysis. 29 June 2016 Japan Meteorological Agency

Transcription

1 Exercise: Satellite Imagery Analysis 29 June 2016 Japan Meteorological Agency

2 Contents 1. Fog/Stratiform Cloud 2. Cb (Cumulonimbus)/Cg (Cumulus congestus) 3. Upper-level Flow Jet stream, upper trough, upper level vortex 4. Lower-level Flow 5. Tropical Cyclones 6. Mountain Waves 7. Volcanic Ash 8. Forest Fires 9. Yellow Sand

3 Determination of Cloud Types

4 Visible and Infrared Imagery Visible imagery Used to determine intensity of reflected solar radiation Used to measure optical thickness of cloud Thin Darker Thick (or dense) Brighter Infrared imagery Used to determine brightness temperature of target objects Used to measure cloud height Low Level Darker High Level Brighter

5 Determination Using Visible and Infrared Imagery Dark Infrared image Bright Dark Visible image Bright Ci Cm Cb,Cg,Cu Sc St

6 Fog/Stratiform Cloud

7 Identification of Fog/Stratiform Cloud Fog/stratiform cloud is dense and forms at very low levels. It appears darker in infrared imagery and brighter in visible imagery. The surface of a fog area is also smooth in visible imagery because it is located immediately below a stable layer. Infrared Visible

8 At Nighttime I4 IR I4 IR 3.9 μm 10.4 μm 3.9 μm 10.4 μm S2 (I4 - IR) Water Cloud Surface Infrared difference imagery S2: I4 (3.9 μm) IR (10.4 μm) 0 <0 Gray White

9 S2 (I4-IR); Fog

10 Cb (Cumulonimbus)/ Cg (Cumulus congestus)

11 Differentiation between Cb and Cg Cb Whiter than Cg in infrared imagery Accompanied by anvil Ci Cg Dotted appearance Anvil Ci Use animation to see movement.

12 Cb/Cg Infrared imagery (The F wedge points to Cb, while the G wedges indicate Cg.) Visible imagery

13 Examples of Cu and significantly developed Cb IR VS A A B B

14 Examples of Cu and significantly developed Cb IR VS A A is Cb A B B is Cu B

15 Anvil Ci Cb Ci Cb Ci Infrared imagery Both taken at 09 UTC on August 3, Visible imagery The distinction of Cb/Ci is important. Cb: heavy rain Ci: NO heavy rain Ci/Cb differentiation is based on texture, movement and location.

16 Differentiation between Cb and Ci All available information from satellite imagery should be utilized in addition to color. Point 1 Form and texture Cb: The windward side is usually clear and distinct. Ci: This is stratiform cloud with a feathering pattern, and appears very white in IR. Cb and dense Ci cannot be differentiated on the basis of form alone. Point 2 Movement and lifetime Cb: Develops/decays rapidly. Cb is stationary or slow-moving. Ci: Flows rapidly to the leeward side due to fast flow of upper air. The lifetime of convective cloud (Cb) is generally shorter than that of stratiform cloud (Ci). Point 3 Location Cb: Develops due to atmospheric instability. Ci: Prevails in connection with upper-layer jets, areas north of cloud bands, the northern side of cyclones and other locations.

17 Upper-level Flow

18 Use of Water Vapor Imagery WV Height [km] Tropopause H 2 O Mixing ratio

19 Purpose of Water Vapor Imagery Analysis Positional estimation for troughs, vortexes, ridges and jet streams in upper or middle air based on the rate of change in bright and dark regions Water vapor imagery, 00 UTC, 17 October 2007

20 Upper troughs are low-pressure areas in the upper layer. They are characterized by downdraft at the back and updraft at the front. In descendent atmospheric conditions: The atmosphere is warmed by adiabatic compressive heating. Relatively dry air comes down from the stratosphere. This makes upper troughs warm and dry, giving them a black appearance in water vapor imagery. height Upper Troughs gray black gray trough Upper trough moist dry Water Vapor imagery, 12UTC, 4 October 2007

21 Boundaries Related to Jet Streams Water Vapor imagery, 00UTC, 8 October 2007 In some cases, jet frontal zones are relatively dry and jet stream zones are relatively moist. This causes the appearance of a boundary in water vapor imagery. Dry = Dark appearance moist moist jet axis

22 Transverse Line Infrared imagery of a transverse line 03UTC, 30 August hpa analysis, 00UTC, 30 August 1998.

23 Jet streams, Upper Troughs, Upper vortices

24 Jet streams, Upper Troughs, Upper vortices Jet stream Upper vortex Upper trough

25 Lower-level Flow

26 Comparison of Visible Imagery and Infrared Imagery Low level = Darker in infrared imagery Middle density = Relatively bright in visible imagery

27 Tropical Cyclones

28 Tropical Cyclones Convective clouds with cyclonic rotation

29 Tropical Cyclone Structure Surface L Coriolis force (Northern Hemisphere) L Cyclonic rotation

30 Mountain Waves

31 Lee Wave Clouds Lee wave clouds are wave-like lower clouds generated along mountain ranges. The wave length is typically km. Lee wave clouds indicate the presence of a stable layer around the mountain-top height and relatively strong winds at this level. visible image at 03UTC, Oct 21, 2007 visible image at 02UTC, Nov 3, 1998 water vapor image at 03UTC, Oct 21, 2007

32 Example of a Lee Wave Cloud visible image at 03UTC, Oct 21, 2007 Lee wave clouds are sometimes accompanied by clear air turbulence in the lower layer. Emagram from observation at Sapporo 12UTC, 21 October 2007 Sapporo stability is neutral under the reverse layer Pilot reports (PIREPs) of turbulence severe moderate plus moderate

33 Orographic Ci Infrared imagery at 03 UTC on Jan 1, Orographic Ci is cirrus generated along mountain ranges. Its upstream edge is sharp and its downstream edge is indistinct. Orographic Ci indicates relatively strong winds in the lower layer (around the mountain-top height) and relatively high humidity in the upper layer. Visible imagery at 03 UTC on Jan 1, 2007.

34 Volcanic Ash

35 Infrared Difference Imagery (IR I2) SP μm (IR) 12.3 μm (I2) Cloud free area SiO 2 Thin Ci Dry Wet Thick cloud Radiation characteristics of quartz (SiO 2 ) Blackbody Volcanic ash and Yellow sand IR1: cleaner window Different transmissivity characteristics IR - I2 ( μm) is 0 Positive =0 Negative Positive ( Gray Black Light gray White Black )

36 Volcanic Ash from Kuchinoerabujima Difference imagery ( μm)

37 Fire Detection with I4 (3.9μm) T fire = 500K Temperature T(3.9μm) T(11μm) Response functions to fire differ between IR1 and IR4 T surface = 300K 0.05 Fire Fraction When 5% of a 300 K pixel is 500 K, 320 K is detected in IR1 (11 μm) 360 K is detected in IR4 (3.9 μm) 320K 300K Less affected IR1 11μm Sub-pixel Effect IR4 3.9μm 1 pixel 360K more affected

38 Volcanic Ash from Mt. Raung in Indonesia Difference imagery ( μm)

39 Forest Fire

40 Forest Fire Hot Spot in Indonesia Difference imagery ( μm)

41 Forest Fires and Smoke in Indonesia Visible imagery

42 Yellow Sand

43 Infrared Difference Imagery (IR I2) SP μm (IR) 12.3 μm (I2) Cloud free area SiO 2 Thin Ci Dry Wet Thick cloud Radiation characteristics of quartz (SiO 2 ) Blackbody Volcanic ash and Yellow sand IR1: cleaner window Different transmissivity characteristics IR - I2 ( μm) is 0 Positive =0 Negative Positive ( Gray Black Light gray White Black )

44 Yellow Sand (Difference imagery) 10.5 μm (IR)-12.3 μm (I2) Yellow sand forecast

45 Exercise

46 Answer the questions. Check Text Questions

47 Drawing

48 Fog/St (1)

49 Fog/St (2) Drag on to the image Select L

50 Cb/Cg

51 Lower-level Flow

52 Drag onto the image Tropical Cyclone

53 Upper-level Flow

54 Upper vortex, trough