Atmospheric sampling of Supertyphoon Mireille with NASA DC‐8 aircraft on September 27,1991, during PEM‐West A

Abstract

The DC-8 mission of September 27, 1991, was designed to sample air flowing into Typhoon Mireille in the boundary layer, air in the upper tropospheric eye region, and air emerging from the typhoon and ahead of the system, also in the upper troposphere. The objective was to find how a typhoon redistributes trace constituents in the West Pacific region and whether any such redistribution is important on the global scale. The boundary layer air (300 m), in a region to the SE of the eye, contained low mixing ratios of the tracer species 03, CO, C2H6, C2H2, C3H8, C6H6 and CS2 but high values of dimethylsulfide (DMS). The eye region relative to the boundary layer, showed somewhat elevated levels of CO, substantially increased levels of 03, CS2 and all nonmethane hydrocarbons (NMHCs), and somewhat reduced levels of DMS. Ahead of the eye, CO and the NMHCs remained unchanged, 03 and CS2 showed a modest decrease, and DMS showed a substantial decrease. There was no evidence from lidar cross sections of ozone for the downward entrainment of stratospheric air into the eye region; these sections show that low ozone values were measured in the troposphere. The DMS data suggest substantial entrainment of boundary layer air into the system, particularly into the eye wall region. Estimates of the DMS sulphur flux between the boundary layer and the free troposphere, based on computations of velocity potential and divergent winds, gave values of about 69 gg S m -2 d-•averaged over a 17.5 ø grid square encompassing the typhoon. A few hours a•er sampling with the DC-8, Mireille passed over Oki Island, just to the north of Japan, producing surface values of ozone of 5.5 ppbv. These 03 levels are consistent with the low tropospheric values found by lidar and are more typical of equatorial regions. We suggest that the central eye region may act like a Taylor column which has moved poleward from low latitudes. The high-altitude photochemical environment within Typhoon Mireille was found to be quite active as evidenced by significant levels of measured gas phase H202 and CH300H and model-computed levels of OH.

A three‐dimensional global model study of atmospheric methyl chloride budget and distributions

“…During the PEM‐West B mission, air samples were collected from February to March 1994. One major feature in the vertical profiles of CH 3 Cl during PEM‐West A (Figures 7‐15–7‐17) is the enhanced concentrations observed at high altitude (above 10 km), which reflect transport of CH 3 Cl by typhoons [ Newell et al , 1996; Blake et al , 1997; Kondo et al , 1997]. The model results show little vertical variation and did not reproduce those elevated concentrations.…”

Long‐range transport of Asian pollution to the northeast Pacific: Seasonal variations and transport pathways of carbon monoxide

“…We also find two convective transport cases during fall 2001 (out of four) where transport in typhoons resulted in export of Asian pollution to the upper troposphere (E1, Table 2). Indeed, Newell et al [1996] and Blake et al [1996] reported elevated concentrations of O 3 , CO and hydrocarbons in the upper tropospheric convective outflow of typhoons during PEM‐West A in the fall of 1991. Springtime convection over SE Asia exports biomass‐burning emissions to latitudes south of 35°N (section 4.2), thus seldom reaching the CPO region.…”

Morphology of the tropopause layer and lower stratosphere above a tropical cyclone: a case study on cyclone Davina (1999)

“…In 1991 the DC-8 sampled the Typhoon Mireille from the boundary layer to the upper troposphere up to 12 km (Newell et al, 1996); the boundary layer eye region showed increased levels of ozone but at higher levels there was no evidencefrom ozone lidar cross sections -of increased ozone from downward entrainment of stratospheric air into the eye upper region; this indeed showed low tropospheric values.…”