Origin and transport of tropical cirrus observed over Paramaribo station

Transcription

1 Origin and transport of tropical cirrus observed over Paramaribo station JGR 2006: Paul Fortuin 1, Cor Becker 3, Masatomo Fujiwara 4 Franz Immler 5, Otto Schrems 5, Rinus Scheele 2, Ge Verver 2 1 DWW, 2 KNMI, 3 Met Office Suriname, 4 Un. Hokaido, 5 AWI Bremerhaven 3rd SOWER Meeting, Lake Shikotsu July, 2006 Paramaribo station - location and seasons - observations (Snow White, Lidar) Results: observations vs. ECMWF Interpretation - transport of cirrus role inertial instability, thermal wind - origin of cirrus (back-trajectories)

2 Paramaribo station 6ºN 55ºW Seasons: - dry: Aug-Nov, Feb-Mar - wet: Dec-Jan, Apr-Jul Observations - sondes: weekly since Sep '99 - SnowWhites: 37 since Oct '02 - Lidar: backscatter Oct-Nov '04

3 Season no. Date Concurrent observatio Height of cirrus (km) Long dry Oct '02 O 3, wind = - (ITCZ to Oct '02 = == = === - north) Oct ' Oct ' = Oct '02 ~O 3, ~wind = == = == Short wet Jan '03 O 3, wind defect Short dry ITCZ to south Feb '03 - ==========? = Mar '03 == ===== = = Long wet Apr '03 - = May'03 - == == - == Short dry (ITCZ to south) Long dry (ITCZ to north) Pilot Study Jun '03 ======= = == Feb '04 - defect Feb '04 - = == = === Feb ' = = == = Mar ' Mar ' = Oct '04 O 3, lidar = == = =- = = ==? Oct '04 lidar = ==== == ====? Oct '04 O 3, wind Oct '04 O 3,V, lidar -- = === = Nov '04 lidar = = Nov '04 lidar - == Nov '04 O 3, V, lidar = = - == = Nov '04 lidar = == Nov '04 lidar = Nov '04 ~lidar == = Nov '04 wind, lidar = == Nov '04 O 3, V, lidar ====== = - Snow White launches

4 Snow White vs. lidar backscatter RH % lidar Pilot Study 15 Oct - 22 Nov '04 Relative Humidity: - w.r.t water, T > 0 ºC - w.r.t ice, T < 0 ºC

5 RH % Snow White/sonde Pilot Study vs. ECMWF analyses RH % T ºC T ºC

6 sonde wind Pilot Study vs. ECMWF U U V V

7 ITCZ: to south to north Annual cycle (average ) Daily ECMWF RH % T ºC V U

8 Annual cycle (average ) Daily ECMWF RH % T ºC V U ITCZ: to south to north

9 Study 2 scenario's: ITCZ to north (Jul - Oct) ITCZ to south (Dec - May) Convective Precipitation

10 ITCZ to the north (Jul - Oct) Dynamic effects on transport: tropopause 12 km - C + C thermal wind: rad. cooling of moist layer southward transport -> E'y Equator U V

11 ITCZ to the north (Jul - Oct) Dynamic effects on transport: thermal wind: rad. cooling of moist layer southward transport -> E'y inertial instability: for PV < 0: N-ward transport E'y tropopause 12 km - C Equator + C U V

12 Inertial instability Inertial instability when: PV (f + ζ) θ < 0 (NH) That is, when - ζ U y > f

13 Inertial instability Inertial instability when: PV (f + ζ) θ < 0 (NH) That is, when - ζ U y > f

14 Inertial instability Inertial instability when: PV (f + ζ) θ < 0 (NH) That is, when - ζ U y > f

15 ITCZ to the north (Jul - Oct) tropopause thermal wind [Fujiwara '03]: rad. cooling of moist layer 12 km - C + C u z g f T T y southward transport -> E'y Equator Paramaribo

16 ITCZ to the north (Jul - Oct) tropopause thermal wind [Fujiwara '03]: rad. cooling of moist layer 12 km - C + C u z g f T T y southward transport -> E'y Equator Paramaribo inertial instability [Fortuin '03]: f f + v x 0 u y < 0 tropopause 12 km - C + C transport E'y northward W'y southward Equator Paramaribo

17 ITCZ to the north (Jul - Oct) Dynamic effects on transport: thermal wind: rad. cooling of moist layer southward transport -> E'y inertial instability: for PV < 0: N-ward transport E'y tropopause 12 km - C + C Equator Paramaribo U V

18 Study 2 scenario's: ITCZ to north (Jul - Oct) ITCZ to south (Dec - May) Convective Precipitation

19 ITCZ to the south (Dec - May) Dynamic effects on transport: 12 km tropopause + C - C thermal wind: rad. cooling of moist layer northward transport -> W'y cool air Equator Paramaribo

20 ITCZ to the south (Dec - May) Dynamic effects on transport: 12 km tropopause + C - C thermal wind: rad. cooling of moist layer northward transport -> W'y cool air Equator Paramaribo dt dz K km V

21 ITCZ to the south (Dec - May) Dynamic effects on transport: 12 km tropopause + C - C thermal wind: rad. cooling of moist layer northward transport -> W'y cool air Equator Paramaribo

22 ITCZ to the south (Dec - May) Dynamic effects on transport: thermal wind: rad. cooling of moist layer northward transport -> W'y inertial instability: for PV < 0, zonal symmetry: stacked cellular flow [Dunkerton '81] 12 km tropopause - C + C cool air Equator Paramaribo

23 ITCZ to the south (Dec - May) Dynamic effects on transport: 12 km tropopause + C - C thermal wind: rad. cooling of moist layer northward transport -> W'y inertial instability: for PV < 0, zonal symmetry: stacked cellular flow [Dunkerton '81] Equator Paramaribo cool air

24 ITCZ to the south (Dec - May) Dynamic effects on transport: thermal wind: rad. cooling of moist layer northward transport -> W'y inertial instability: for PV < 0, zonal symmetry: stacked cellular flow [Dunkerton '81] 12 km tropopause - C + C cool air Equator Paramaribo U V ITCZ: to south to north

25 ITCZ to the south (Dec - May) Dynamic effects on transport: thermal wind: rad. cooling of moist layer northward transport -> W'y inertial instability: for PV < 0, zonal symmetry: stacked cellular flow [Dunkerton '81] 12 km tropopause - C + C cool air Equator Paramaribo U V

26 Origin of cirrus 5-day back-trajectories ECMWF: from: SnowWhite Ci event (if corresponding 100% RH ECMWF ) until: deep convection + increase cloud cover & cloud ice content ITCZ to north (Jul - Oct) ITCZ to south (Dec - May) Convective Precipitation

27 Origin of cirrus ITCZ to north (Jul-Oct) ITCZ to south (Dec-May) Ci in TTL km Ci in outflow km

28 5-day backtrajectories ITCZ to the south trajectory pressure:

29 5-day backtrajectories ITCZ to the south convective precipitation: trajectory pressure:

30 5-day backtrajectories ITCZ to the south convective precipitation: trajectory pressure: cloud cover:

31 Conclusions Good agreement Ci from Lidar vs. Snow White (vs. ECMWF) 2 apparent features Ci over Paramaribo: - annual cycle in height Ci: ~ 17 km Dec - Mar ~ 15 km Jun - Sep - almost all Ci comes from north this is due to: - intensified B-D circulation Dec - Mar - inertial instability flow, cell above Hadley cell 2 dynamical processes important in transport of moist air/ci: thermal wind inertial instability ITCZ to N: southward -> E'y jet N of E'y jet, norhtward transport ITCZ to S: northward -> W'y jet 0-10ºN UT, stacked cellular flow Origin of Ci: - from ITCZ to N, deep convection inland - from ITCZ to S (via sec. circulation cell), deep convection elsewhere

32 Arigato gozaimasu!