Macquarie Island (54.6 S, 158.8 E)

Meteorological Records dating back to 1948 Surface observations Can be found at http://www.bom.gov.au/climate/data/?ref=ftr Observations have been used for a variety of studies Adams (2009) reported a 35% increase in precipitation from 1970-2008 (predominantly in winter.) Hande et al (GRL 2012) reported surface winds increasing a ~3 cm/s/year from 1991-2011.

Light precipitation (P < 0 Light precipitation (P < 0.066 mm/h) is common at Macquarie Island for observations, ERA-I and CloudSat. Strong precip (P > 1 mm/h) commonly associated with frontal activity (although the definition of fronts is not that consistent.) The standard CloudSat precip product often records ice or mixed phase, especially in winter (no quantitative precip available.)

Previous Field Observations Russell et al. (1998) identifies a ‘buffer layer’ above the boundary layer during ACE-1. Jensen et al. (2000) identifies an ‘intermediate layer’ above the boundary layer during SOCEX II.

Can we identify a ‘buffer layer’ in the soundings from Macquarie Island? What about the ECMWF operational analysis for the Year of Tropical Convection (YOTC)? Soundings: Low resolution Data interpolated on to standard levels plus additional levels at inversions 1973-2011 High Resolution: 10 second vertical resolution 1995-2011 YOTC ECMWF operational analysis 2008-2010

Example of a decoupled boundary layer with shear over the secondary inversion (ie. a buffer layer). Hande et al. (JGR 2012) MAC YOTC

Boundary Layer Height BL height: primary inv 0.01 K/m 84.4% of MAC 52.3% of YOTC MAC median = 1278 m MAC std = 624 m YOTC median = 1050 m YOTC std = 524 m

Height of Secondary Inversion BL height: secondary (decoupled) inv: 0.005 K/m 66.6% of MAC 22.7% of YOTC MAC median = 680 m YOTC median = 734 m

Soundings normalized to the primary inversion MAC YOTC Compared to the YOTC, the MAC boundary layer is, on average: more stable has weaker winds less shear

Boundary layer classification: Type 1: No significant inversion Type 2: Single well mixed layer with 0.01 K/m Type 3: A ‘decoupled’ BL with no shear across 2nd inversion ( 0.005 K/m) Type 4: A ‘decoupled’ BL with shear over secondary inversion (I.e. ‘Buffer Layer’)

How does resolution affect the statistics? Type 1: No Inversion Type 2: Single Inversion Type 3: Secondary Inversion Type 4: Buffer Layer MAC 15.6 17.8 32.9 33.7 MACp ave 34.2 42.1 14.1 9.6 2008 – 2010 31.8 45.2 12.4 10.6 YOTC 47.6 29.6 20.6 2.2 Add to above slide