Local Boundary Layer phenomena & flux estimation in LBA2ª Reunión Nacional de Ciencias de la Tierra UNIÓN GEOFÍSICA MEXICANA

David FitzjarraldJungle Research GroupAtmospheric Sciences Research CenterUniversity at Albany SUNY, US of A

Otávio AcevedoMatt CzikowskyJeff FreedmanRalf StaeblerGary Wojcik

Ricardo SakaiKathy MooreDwayne Spiess

Precipitation in central Amazon is highly seasonal (from Mendes, MS thesis UFPa, 1999)

But the rainfall at the riverside

climate stations is biased. (Garstang & Fitzjarrald, 1999, p. 290)

Rainfall between 4/16 & 5/14/87, ABLE 2b.

Rio Solimões

C flux observations will always be biased by local circulations.Which is more important--”LULC” or river effects?

Confluence of the Tapajos & Amazonas rivers near Santarém.

It is nowhere flat, especially at night.

Topography in the LBA-Ecology region near Santarém.Weather station & flux tower sites indicated.

It is nowhere homogeneous.

Surface type categories in the FLONA Tapajos River is at left.

It is always awkward to do field work at “remote” sites.

LBA-Ecology PastureSite (km 77)

Solar panels

Tower

Automatic weather station at Belterra. Tapajós River in background.

Automatic weather station at Fazenda Caboco, km 117.

“Humble” but continuous, long-term data should be highly prized.(But remember that information goes both ways between modelers & observers.)

Automatic weather stations near Belterra (top) and at Fazenda Caboco, km 117 (bottom). JRG, ASRC

Sample time series from the Belterra automatic weather station.

With enough data, you can select for the periods for which anybudget methods might be most applicable. (Isolated case studies may lead only to anecdotal information.)

On light wind days, the river breeze leads to WD reversal.

Wind vector by hour of day (LT). Reversal of wind a Belterra occurs primarily on windswith suppressed easterlies. Wind reversal at Km117 occurs at night with very light

winds, indicative of a shallow drainage flow in the pasture.

“Hodographs” made by hour (local time) are useful,if you can wait to get a large enough data set.

(after Simpson, 1994) Satellite image in the Amazon region, showing dense field ofcumulus clouds, interrupted by the influence of the Oronoco River

Visible GOES image(recorded at USP)

IR GOES

1999LBA-EcologyJRG & USP

Average low cloud frequency for May 1999.with the station network, we get areal distribution of incident radiation. Lookslike “subtle” topographycan be important in the humid tropics.

Freedman & Fitzjarrald (2000)

Recovery from synopticDisturbance--fair weatherClouds drive the system toA preferred LCL (or RH).

Freedman & Fitzjarrald (2000)

Synthetic Aperture Radar image of Chesapeake Bay drainage flows. (Winstead et al., 1997).

AIRSHEDS!.Drainage outflows seen from “ripples”on a calm morning.(Maryland, US of A)

Land

Water

Lots of things go on inside the rain forest canopy.Vertical profiles at Ducke (Fitzjarrald et al., 1988)

Something completely different. Prototype of the in-canopysounding system, improving on the G. Parker (right) design. T, q, [CO2]

Observing very local scale advective effects may not be possibleif there are no regular local flows to provide a periodic signal.

Test observations done by JRG at Harvard Forest (Staebler et al., 2000).

Which way is uphill?

Effects of the local hillextend well into the SBL.(SODAR results and mysteries!)

HF, DRAINO (Staebler, JRG).

Utility of SODAR observations.It doesn’t measure quite what we want.

At Harvard Forest...

What we need to do:

• Use data compositing creatively.

• Deploy remote sensing instruments to get the BL winds (e.g. profilers and acoustic sounders) and concentrations (e.g. DIAL) in horizontal arrays. Operate these networks for several seasons continuously.

• Develop hybrid schemes using continuous time series from surface data. Select data for transient periods of weak turbulence and estimate surface flux from ∂C/∂t; use bounding value (envelope) analyses for guidance; take advantage of the early evening, morning transitions.

• Do not ignore the role of clouds. Their presence drives the BL toward constant relative humidity equilibrium. Also, cloud base gives an estimate of CBL thickness--can use ceilometer.

• Exploit the nocturnal case.(!) Use the regularity of local winds to find the advection terms. Such “natural” boxes as an alpine valleys provide predictable circulations ideal for making composites. Drainage flows from coastal areas carry respiratory CO2 from airsheds over water. Measuring the volume of the outflow and its excess [CO2] allows an independent estimate of the forest respiration rate.