The internship of the author is examined in detail. The acquisition of the internship, the personnel of the project, the project itself, and the goals associated with it are described. The authors orientation to the internship, the project's operations, and the conclusion of the findings are also described. The overall goal of the project was to determine the effect of convective waves on wind speeds in the middle and upper troposphere, and how these waves affect the general circulation on a global scale. A more specific goal of the author was the satellite analysis of cloud street formations. This was done to determine frequency and areas in which cloud streets occur off the East Asian and North American coastlines

Collins, Charles

Rademacher, Kurt R.

English

NASA Technical Reports Server

Review of Geography
Internship on Convective Wave Project
by
Kurt R. Rademacher
Dr. Charles Collins
Univ. of Northern Colorado Geography Department
(_ASA-CR-]6)?O?2) REVIEW _F GFOGRAPHY
INTrRNDHIP OF CnNVZCTIV_ WAVE PROJECT
(University of Northern Color_Jo) 13 p
CSCL 08G
G3/46
N91-I_819
Uncl_s
0304607
https://ntrs.nasa.gov/search.jsp?R=19910004506 2020-03-19T20:54:11+00:00Z
I. Introduction
The purpose of this paper is to examine in detail my internship for
the University of Northern Colorado, fall semester of 1989. I will describe
the acquisition of the internship, the personnel of the project, the project
itself and the goals associated with it. I will also describe my orienta-
tion to the internship, the project's operations, and the conclusion of the
findings.
I initially contacted the University of Colorado's Geography
Department during May of 1989 to discover any possible internships available
to students from other universities. At the time I was attending California
State University at Northridge, through the National Student Exchange
program of which U.N.C. is a member. Knowing that I wanted to reside in
Boulder, I was interested in an internship in the area. I was informed by
the C.U. Geography Department that I would only be able to choose from those
internships that were not filled by C.U. students. I made note of one
internship entitled "Convective Waves Project," from a Dr. Robert Grossman
of CIRES (Cooperative Institute for Research in Environmental Sciences),
University of Colorado, Boulder. He was looking for one or two interns for
the summer and fall semesters. When I returned to Colorado in August of
1989, I met with Dr. Charles Collins of the U.N.C. Geography Department. I
was seeking his approval of an internship through the C.U. Geography
Department. After receiving Dr. Collins' approval, I interviewed for the
internship with Dr. Grossman and had my transcripts from U.N.C. and C.S.U.N.
sent to CIRES. I also referred him to the C.U. Geography Department to read
letters of recommendation from a few of my former geography professors.
Introduction
a. Acquiring the Internship
b. Personnel
c. Convective Waves
Project Goals
a. Overall Project Goal
b. Specific Goals of Cloud Street Satellite Project
c. Goal of Analysis and Digitization
Orientation
a. Introduction to Internship
b. Introduction to CIRES
c. Introduction to Data and Materials
Project Operations
a. Analysis of Individual Days 1:30,000,000 Polar Sterographic
b. Photocopying and Retrieval of Data
c. The "Atotal" Program
d. PermanentStorage of Data
e. Contouring and Modifying "Atotal" Results to Produce Final carto-
Graphic Product
Conclusion
a. Major N. HemisphereCloud Street Areas
b. Frequency of Occurrence and Area
c. Speculations on Recent Climate Variability
2Since this process took sometime it was about a week into U.N.C.'s fall
semester when I was accepted into the internship.
The internship took place at CIRES, which is a branch of the
University of Colorado's Boulder campus. I worked under the direction of
Dr. Robert Grossman who is with CIRES, and Dr. Joachim Kuettner who is with
NCAR (National Center for Atmospheric Research). I worked most closely with
Dr. Grossman, who is located in Research Laboratory-2; this was the same
building I worked in. I also worked with Kurt Van Speybroeck, an intern
from the University of Colorado's Geography Department. He had worked with
Drs. Grossman and Kuettner for the summer semester and was continuing his
internship into the fall semester.
When I was read the description of the internship over the phone I
did not fully comprehend what a convective wave was. I was familiar with
mountain waves and the lenticular clouds associated with them, but I needed
more information on what Drs. Kuettner and Grossman were researching. The
difference between convective waves and mountain waves was found to be that
the former occur over flat terrain. Convective waves are internal gravity
waves that are within the troposphere (and possibly stratosphere) generated
by a convectively active boundary layer (Grossman, 1989). Convective waves
were first discovered and utilized by glider pilots. These waves enable
sailplanes to climb upstream of cumulus clouds well above cloud tops (see
Figure I).
Convection waves are a strong function of the original forcing by
convection in the boundary layer. This convection can take the form of
random or two-dimensional spatial structure. When clouds are formed as
a result of two-dimensional boundary layer forcing (horizontal roll
vortices) they are called cloud streets. Cloud streets when formed
under conditions of cold or warm advection (which account for necessary
shear) provide a very strong forcing for convection waves since the
streets act like a periodic obstruction to the flow, enhancing the
formation of waves. (Grossman, 1989)
For our purposes, research of cloud streets focused on the coasts off East
Asia and Eastern North America, during the winter season. That is the time
when very cold dry air, originating from the Arctic, descends over the
continents and flows over the Kuroshio (Japan Current) or the Gulf Stream.
These warm water currents and their relative locations off the continents
make the atmosphere over them favorable for formation of convective waves,
and cloud streets (see Figure 2).
II. Project Goals
After this somewhat detailed description of convective waves and the
important cloud street formation associated with them, I will now address
the convective wave research project goals, and how my internship helped to
achieve some specific goals. The overall goal of the project was to
determine the effect of convective waves on wind speeds in the middle and
upper troposphere, and how these waves affect the general circulation on a
global scale. "Internal waves have the potential of extracting westerly
momentum from the atmosphere. Present forecast modes consistently overesti-
mate westerly winds and this is one of the limits to accurate numerical
weather and climate forecasts" (Grossman, 1989). This is important to note
because the wind speeds of the jet stream are probably affected by convec-
tive waves. A more specific goal of the project which my internship focused
on was the satellite analysis of cloud street formations. This was done to
determine frequency and areas in which cloud streets occur off the East
Asian and North American coastlines. I also noted other areas in the
• L
4
Northern Hemisphere where cloud streets occur. This research will assist
global numerical forecast models, aircraft investigation off the east coast
of North America, and provide cartographic results showing frequency and
areas of cloud streets during a given time period.
Ill. Pro_ect Orientation
When I began my internship I needed to be oriented to the various
aspects of the internship. First I was introduced to the project, and the
work I would be doing. Second, I was oriented to the CIRES organization and
building, RL-2 where I would be working. Third, I was oriented to the data
I would be using and the materials used.
Dr. Grossman spent some time with me each day during the beginning
of my internship orienting me to the project and work I would be involved
with. Kurt Van Speybroeck was not present when I began due to his absence
from the country. This proved to be somewhat of an inconvenience for Dr.
Grossman and myself, but Dr. Grossman resolved this by having me work on
jobs that had already been completed by K. Van Speybroeck. He also gave me
materials on convective waves to read. I also used Dr. H. Reihl's "Intro-
duction to the Atmosphere" for basic meteorological concepts I needed to
understand. Dr. Grossman checked my work and compared my results with K.
Van Speybroeck's. He continued to check my work at regular intervals
throughout the duration of the internship.
I was also oriented to the CIRES organizational structure by Dr.
Grossman. He showed me where I would be working; also where I would find
some materials and support I might need, including the front office. My
orientation to data and materials was also critical and handled by Dr.
5Grossman. The National Snowand Ice Data Center (NSIDC), located here at
RL-2 has established a collection of satellite imagery acquired from the
United States Air Force Defense Meteorological Satellite Program (DMSP).
DMSPis a system of near-polar orbiting satellites providing information in
two spectral bands, visible and infrared. This was the data source used
during the internship. Dr. Grossmanalso introduced me to the materials I
would be using to accompanythe satellite data. WhenKurt Van Speybroeck
returned, he oriented meto the Numonics2300 digitizer and the 855 computer
commandsI would be using. He also went over somefine details I would need
to makemy work efficient and productive.
IV. Project Operations
After being oriented to the project, CIRES and the data and mate-
rials I would use, I was instructed on how the actual work was done, from
research analysis to the final cartographic display. I will now detail each
step and give any pertinent information that was useful in the internship
and project. Those steps were analysis of individual days, photocopying,
digitizing and retrieving data, running the "atotal" program, permanent
storage of data, and finally contouring and modifying the "atotal" results
that produced the final cartographic product.
The first step of the process was analysis of individual days using
the DMSP 1:30,000,000 polar stereographic projections. These mosaics are
compiled from several orbital strips and have a resolution of 5.4 km.
Visual mosaics were primarily used for analysis. However, since cloud
streets are a low-level phenomenon, infrared images were used to discrimi-
nate between cloud streets and high level gravity-wave clouds, which have
6the samevisual appearance as cloud streets. Infrared mosaics were used
when visible mosaics were missing. Each day had two separate analyses; one
for the North American continent's coastline and one for the Asian coast's.
The satellite image was backlit on a light table and a mylar overlay with
the coastline and latitude, longitude locations critical to alignment were
matched to each other. The areas of cloud streets were noted as well as the
date and time of their occurrence. Whenworking on already-completed
analysis for December1985, I noticed mistakes in the time zone figurations.
This madethe analysis one day off in this month for the Asian analysis. It
was critical to figure howmanyhours to add or subtract from Greenwich time
according to the time zone the cloud streets were located in, and when the
satellite image was taken.
Whenresearching and noting cloud streets on the mylar overlays it
was important to photocopy each day for a permanent record. After one month
had been analyzed and each mylar had been photocopied, the china marker that
is used for analysis was cleaned off the mylar for reuse. Digitizing was
the next step in the process. Eachmylar overlay has a three-point set-up
for use with the digitizer, and I should note that all the preliminary work
had already been done by K. VanSpeybroeck during his summerinternship.
This allowed me to concentrate on analysis and digitizing during my intern-
ship since muchof the preliminary research work had been completed. The
digitization process takes the cloud street information analyzed in polar
stereographic form and converts it to a usable mercator projection form.
This information was stored in data files on the NOAA855 computer. To
begin digitizing I logged on to the terminal hooked up to the Numonic2300
digitizer and created a file for each day of the month for both the North
American and Asian continents. For the exact process of digitizing see
attachment I. The continent's printouts for each day were sent to the laser
printer located in the World Data Center's computer in RL-2. About five
files at a time were sent to the printer in order to avoid tying up the
printer for long periods.
After the entire month had been digitized an "atotal" program was
run. This program sumsall the days of the month and plots the areas in
which cloud streets have occurred. The "atotal" program was run for each
continent. The crude cartographic result was printed out and then enlarged
on a photocopier to 130%. This was saved for later analysis and modifica-
tion.
The digitized data files were permanently stored on floppy disks by
entering the 855 computer and accessing the Kermit editor. The Kermit
editor rejects bad data and will notify the user of any system failure.
Files were stored on disk and purged from the 855 computer whenthe "atotal"
program had been run and completed.
The final step in the process was modifying the "atotal" result in
production of the final cartographic product. As I have noted, the 130%
photocopied enlargement was used to draw contour intervals around and
between the areas in which cloud streets occur. This is a dasymetric
surface with a contour interval of four days. K. Van Speybroeck had
produced someoverlays of the latitude, longitude lines that also included
the coastlines. These were to be used to match up to the 130%"atotal"
enlargement. After all the proper enlargements were lined up, and the
latitutde, longitude lines were drawn, the final mapwas reduced to fit on
an 8 1/2" x 11" format. While inspecting somecompleted final maps, I
noticed errors in the longitude lines, so I did not use the overlays
produced for my own final maps. I have this as a project for the future.
also noticed that a previous method of depicting the dasymetric surface was
incorrect. The maps used varying textures instead of tones to show the
stepped statistical surface. I did manage to produce an incomplete, but so
far correct, cartographic product for the internship and have included it
within this paper. I also have included one of the earlier versions of the
final maps.
8
V. Conclusion
In conclusion I will focus on how the internship influenced the
convective wave project by verifying major Northern Hemisphere cloud street
areas, and noting their frequency of occurrence and area. I will also note
the influence of convective waves and how they are used to speculate on
recent climate variability.
It can be noted with accuracy that the two areas under study, North
America's and Asia's coastlines, are ideal for convective wave research from
November through February. I would estimate that within our research area
cloud streets were documented 80%-90% of the time.
Other areas in the Northern Hemisphere are also worth recognizing
for cloud streets. These are the Barents, Bering, Norwegian and North Seas,
and also the East Atlantic Ocean in the mid to high latitudes. Occasionally
cloud streets occur in the stratus off Southern California and the Baja
California Peninsula. Cloud streets sometimes occur over unusual areas or
9only once in a while over some areas. I have noted their occurrence over
the Black and Caspian Seas, as well as the Red Sea and Bay of Bengal. This
would indicate a very cold and strong air outbreak from the continent
reaching over long distances and/or strong air-sea temperature differences.
Occasionally during large outbreaks over the East coast of North America the
cold air reaches out over the Gulf of Ftxlco and streets form. This
phenomenon, associated with low temperatures in the Gulf Coast States, is of
special interest to Dr. Kuettner. I may be focusing on diurnal variation of
cloud streets in the Gulf in the future.
Climatological maps of sea surface temperature (SST) and sea level
pressure were supplied by Dr. Joe Fletcher, who directs the NOAA Environ-
mental Research Laboratories. These maps assist us in speculating on recent
climate variability. Figure 3 shows two areas in the Northern Hemisphere
which had significantly cooler SSTs in the period 1971-1987 compared to
1954-1971. These areas of cooler SSTs are nearly co-located with areas of
maximum occurrence of cloud streets. Since cloud streets are associated
with cold air outbreaks and large fluxes of thermal energy from ocean to
atmosphere (Grossman and Betts, 1990), these areas of lower sea surface
temperatures may reflect either more intense and/or more frequent cold air
outbreaks during the 1971-1987 period compared to the 1954-1971 period.
Cold air outbreaks over warm water currents cool the sea surface temperature
by evaporation, the transfer of sensible heat, and by mixing of the warmer
surface water with the cooler water below. Fletcher's sea level pressure
map (Figure 4) is consistent with the hypothesis that cold air outbreaks
were more intense in the 1954-1971 period rather than more frequent. Higher
10
pressures would be associated with stronger cold air outbreaks rather than
more frequent ones, whose pressures may not have changed much from one
period to the next. Therefore, the co-location of maximum SST cooling and
higher pressures is consistent with an hypothesis of more intense cold air
outbreaks. Lower SSTs are co-located with higher sea level pressures off
the Asian coast near Japan. The situation is different, however, off the
North American coast. There are two distinct areas of high and low pressure
bisected by the 0 line located in the mid-Atlantic Ocean. The area of high
pressure shows the area of cold air outbreaks and cloud streets while the
area of low pressure indicates the area where the storm tracks lie.
Deepening cyclones, as they move out to sea, also extract large amounts of
thermal energy from the ocean. The North American SST cooling may be the
result of air-sea interaction associated with cold air outbreaks and the
preceding cyclonic storm. Our combined research will continue to look into
this intriguing set of observations.
11
VI. Works Cited
Defense Meteorlogical Satellite Program DMSP. "Data Announcement."
National Snow and Ice Data Center. National Geophysical Data Center,
NOAA, Boulder, CO, 80303, 1987.
Fletcher, Joe. "Sea Surface Temperature and Pressure Maps." National
Center for Atmospheric Research (NCAR) Research Laboratories, 3215
Marine St., P.O. Box 3000, Boulder, CO, 1990.
Grossman, Robert. "Flight Operations for Convection Waves Project Cloud
Street Experiment." Cooperative Institute for Research in Environmental
Sciences (CIRES), University of Colorado, Boulder, 1540 30th St., RL-2,
Boulder, CO, 1989.
• "Aircraft Investigation of Gravity Waves Initiated by Convec-
tively Active Boundary Layers." CIRES, University of Colorado, Boulder,
1540 30th St., RL-2, Boulder, CO, 1989.
Kuettner, Joachim, Peter A. Hidebrand and Terry L. Clark. "Convection
Waves: Observations of Gravity Wave Systems over Convectively Active
Boundary Layers." National Center for Atmospheric Research (NCAR), P.O.
Box 3000, Boulder, CO, 1986.
Van Speybroeck, Kurt. "Review of Internship on Cloud Street/Convective Wave
Project." CIRES, University of Colorado, Boulder, CO, 1989.


Review of geography internship of convective wave project

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