Hello and thanks for reading this,

We have an observatory on top of a mountain and I notice
that the wind speed is above the radiosonde winds and NAM 40Km
prediction for this location. I also observe 5 to 15 minute oscillations
in the wind speed and some times also see this in dew point.

Is it possible to relate the ridge geometry cap inversion height to the
speed up factor, radiosonde lapse rate, oscillation frequency and
percent variation in wind speed to estimate the vertical scale size of
the mountain influence ? (mtn outer scale ?)

I assume what I am seeing is atmospheric gravity waves and related Mtn
wave phenomena.

I also see periods in the same range of the wind oscillation in the
optically significant turbulence.

My guess is I will need to use RAMS or the like to investigate the
dependence of all this.

Is there a RAMS modeler in the group that can help me start the model ?

Thanks for your time

Dan McKenna

Dan Mckenna wrote:
Hello and thanks for reading this,

We have an observatory on top of a mountain and I notice
that the wind speed is above the radiosonde winds and NAM 40Km
prediction for this location. I also observe 5 to 15 minute oscillations
in the wind speed and some times also see this in dew point.

I'm not sure there is any reason to expect NAM 40km winds
to agree with winds at a point, especially on top of what
I presume to be an isolated peak. I also assume the
radiosonde is removed from the mountaintop site? (Are you
talking about Kitt Peak? Am I? )


Is it possible to relate the ridge geometry cap inversion height to the
speed up factor, radiosonde lapse rate, oscillation frequency and
percent variation in wind speed to estimate the vertical scale size of
the mountain influence ? (mtn outer scale ?)

I assume what I am seeing is atmospheric gravity waves and related Mtn
wave phenomena.

Yes, that's a fair assumption.


I also see periods in the same range of the wind oscillation in the
optically significant turbulence.

My guess is I will need to use RAMS or the like to investigate the
dependence of all this.

Is there a RAMS modeler in the group that can help me start the model ?

Thanks for your time

Dan McKenna


You should be able to compute a Brunt-Vaisala frequency and
compare it to the observed oscillations in wind speed/dewpoint.
If gravity waves are the culprit, there should be some
similarity between the two time scales. The difficulty, of
course, is getting the suitable temperature/wind profile
for the scale of interest. No modeling would be necessary.


Scott, not a RAMS modeler

Scott wrote:
Dan Mckenna wrote:

Hello and thanks for reading this,

We have an observatory on top of a mountain and I notice
that the wind speed is above the radiosonde winds and NAM 40Km
prediction for this location. I also observe 5 to 15 minute oscillations
in the wind speed and some times also see this in dew point.


Looking at The ready site and using safford as the grid point
evaluating at 700 mb The correlation with temperature, RH, wind trend,
cloud cover and precip is the best I have found.

When gradients are low, i.e. no troughs around, I would expect
a fair correlation between radiosonde and Mtn observations.
This should be true when the flow is in line with Tucson to Mt Graham.
I obtain my one radiosonde data from time to time and have tracked
the ascent moving over or in line with our site.

I'm not sure there is any reason to expect NAM 40km winds
to agree with winds at a point, especially on top of what
I presume to be an isolated peak. I also assume the
radiosonde is removed from the mountaintop site? (Are you
talking about Kitt Peak? Am I? )

Mt Graham Az VATT

Is it possible to relate the ridge geometry cap inversion height to the
speed up factor, radiosonde lapse rate, oscillation frequency and
percent variation in wind speed to estimate the vertical scale size of
the mountain influence ? (mtn outer scale ?)

I assume what I am seeing is atmospheric gravity waves and related Mtn
wave phenomena.


Yes, that's a fair assumption.


I also see periods in the same range of the wind oscillation in the
optically significant turbulence.

My guess is I will need to use RAMS or the like to investigate the
dependence of all this.

Is there a RAMS modeler in the group that can help me start the model ?

Thanks for your time

Dan McKenna


You should be able to compute a Brunt-Vaisala frequency and
compare it to the observed oscillations in wind speed/dewpoint.
If gravity waves are the culprit, there should be some
similarity between the two time scales. The difficulty, of
course, is getting the suitable temperature/wind profile
for the scale of interest. No modeling would be necessary.


Yes I have done that but there is considerable modification
of the nocturnal atmosphere due to radiation and flow effects.
This is also complicated but the Gravity waves in the tree
canopy. I have measured this using a 3 D sonic anemometer and fine
wire probes.

(Just a guess from reading popular science magazine)
Scott, not a RAMS modeler

Dan, not a atmospheric scientist.

Hi Dan,

You may be experiencing the Bernoulli Effect where the atmosphere is
getting sqeezed over the mountain peak causing the stream flow to
compress, and this can cause an increase in wind speed.

Smerby
accuweather.com

Yes, and what I would like to know,
can I use any of the parameters listed in my original post to understand
how high the cap inversion is that is putting the squeeze on the flow

Dan


wrote:
Hi Dan,

You may be experiencing the Bernoulli Effect where the atmosphere is
getting sqeezed over the mountain peak causing the stream flow to
compress, and this can cause an increase in wind speed.

Smerby
accuweather.com