Evening and nocturnal winds in the Hudson valley David R. Fitzjarrald1, Jeffrey M. Freedman2, Ricardo K. Sakai1, Mathew J. Czikowsky1, and Jessica Neiles3

1. Atmospheric Sciences Research Center, UAlbany, SUNY2. Atmospheric Information Services, Albany, NY3. NWSFO Wilmington NC

a look at the decaying CBL in the Hudson valley

partial nocturnal disconnection of surface and SBL

detect presence of a little nocturnal jet.

{ All above illustrated with examples from HVAMS,Hudson Valley Ambient Meterorology Study }

The Hudson ValleyALBCatskillsHudson ValleyKingstonNYCHPNPOU

(Acevedo & Fitzjarrald, 2001, 2003)Old news--stations in the FOG-82 program Albany NY- 26 Stations at the Albany region: moderately complex terrain and thepresence of obstacles (trees and buildings)

The early evening transition (EET) marks the transition from horizontalhomogeneity to heterogeneity in the surface layer.Spatial variability: at any minute, the standard deviation of the values at 26 stationsTemporal variability: at one station, the standard deviation of groups of 30 minutes

Fitzjarrald and Lala, 1989Hudson Valley fog environments, JAM 28,1303-1328.

Model version, Zeman, 1979Cartoon version (Stull, 1988)

*Surface hodograph rotationNamibia (19 S)Alaska (60N)Amazon (3S)NB: all that rotates is not due to theCoriolis effect

The simple-minded approach, temporal spiral towardThe geostrophic point

Typical LES domainHVAMS intensive field obs, 10-11/2003

ISSF station at Green Acres AirportPAM

Zena Cornfield(Station 7)NorthEastWestSouth

PAM Station Network Windroses and Transmission Factors

0600 - 1800 LT

1800 - 0600 LT

Table 1 CBL conditions on case study days.

Date

Hmax

t(Hmax)

t(H0)

zi

w*max

zi/w*

ms-1K

Hour

Hour

m

ms-1

min.

10/6/03

0.087

11.12

17.37

1069

1.46

12.2

10/8/03

0.099

11.87

16.46

1537

1.71

15.0

10/13/03

0.102

12.54

16.62

1521

1.71

14.8

10/18/03

0.052

12.46

16.79

1452

1.35

17.9

10/24/03

0.096

11.46

16.79

1893

1.83

17.2

10/30/03

0.074

12.62

16.71

1473

1.54

15.9

Flights made at specifiedfractions of the mixed layerheightSensible heat flux dies,killing mixing

Q*

Q - Qo Net radiative fluxSensible heat fluxPotential temperature departure

CO2concentrationfluxLeft to do--what kind of CO2advection/entrainment combo.can cause this?

[t* -t*(Hmax) ] -1.2sw/w*2Key result, mixing invertical dies at sunset,but horizontal wind variationpersists into the night.

What do surface stations see at night in thecomplicated landscape of the Hudson valley?

Van de Wiel et al., 2002McNider et al., 1995, MM5 resultsSome problems with how models deal with nocturnal conditionsAre we in the mathematically ambiguous zone?Pulsed mixing, but with a caveat

VERTICAL STRUCTUREBlack: maximum surface T or qblue: T or q at station 1squares: T or q at 30 m (soundings)triangles: T or q at surface (soundings)The value at 30 m from the soundings is in excellent agreement to themaximum surface values observed in the network. Mixing can bring a sheltered point to a regionally characteristic value.(Acevedo & Fitzjarrald, 2001, 2003)

When turbulence restarts at a station, its surface temperaturegoes up to the value observed at the higher, windier stations.The maximum surface value can be used as an approximation to thetemperature at the height to which the surface connects duringturbulence breakdownsAcevedo & Fitzjarrald, 2001, 2003

HVAMS reveals similar signal, but over a wider region

Along-valley wind maximum observed intermittently at the sfc on the east side of the river at higherSites--leads one to seek theHypothesized jet-like structure atLow (50-100 m) along the valley.

Fitzjarrald and Lala, 1989VUqsatqShallow along-valley jet-like circulations appear at night in the Hudson Valley.Along-valleywindTethered balloon results from 1982 obs at Albany airport.

Jet-like feature seen during HVAMS in the early morning..

close approaches to 5 small airfields Surface stationelevations

Missed approach to Green AcresAirport, Oct. 17, 2003, 1300 UT(0900 LST)VUAircraft altitude

October 30, 2003 case..

10/30/03Close approachesAlong valleyCross valley

Not a classicSBL, but also thereis an accumulationlayer that dependson local effects.

Qq

The effect of the density interface at the top of the SBL made visible by a cement plant plume (west side of river),October 17, 2003. Photo by King Air pilot Thomas Drew.

Profiles made from close approaches, 10/17/2003 1242-1307 UTCO2UVQ

No low-level NS wind maximum detected by the NOAA profilerat Schenectady airport L

Southerly component not observed by profilerHard to see the low level jet feature in profiler observationsat Kingston-Ulster airport.

Time series from TAOS10/16/03 18-23 LST

Easterly flow in the early evening

ASRC sodar atSchodack IslandState ParkSoutherly flowappears only in theearly morning hours.

So weve not got it all sorted out yet. Still have to do:

find the pressure gradients that drive the nocturnal jet.

seek the wind rotation in the decaying CBL in the profiler &sodar records.

quantify how landscape and topographic structure are connectedto microclimate and mixing frequency at sfc stations.

figure out how there can be an SBL at all if sfc stations all decouple!(decide where the mixing hot spots are in a landscape.)

What to do about forecasting the Hudson very low level jet:

detailed modeling maybe not yet possible(high resolution needed over large region.)

modeling through grotesque parameterization(always briefly satisfying, but)

continued study of profilers, seek ideal spots forongoing simple observations(sodar, tall towers, profilers).

HVAMS is supported by NSF grant ATM0313718.Jeff Freedman, Matt Czikowsky, Ricardo Sakai, and Alex Tsoyref, the HVAMS team..

Special thanks to Jessica Neiles, Project assistant during the intensive field phase.Undergraduate students Kim Sutkevich, Jason Herb, and Aaron Feinberg assisted both duringthe field operations and in subsequent data analysis when they were joined by Matt Doody.

We thank the teams from U. Wyoming, (especially Larry Oolman, pilot Tom Drew)NCAR ATD (Steve Oncley, Kurt Knudson, Tony Delany and many others), and U. Alabama HuntsvilleMIPS team for their help.