Conditions for Natural Cirrus Cloud forming in Finland in November

See also Jokoinen November 12 & November 13 2012 & Temp      RH for Cirrus form     Altitude Nov. Finland
-40C90%RH7.300m  = 60% RH -40C
-45C85%RH8.000m = 26% RH -45C
-50C80%RH8-9km = 34-15% RH -50C
-55C75%RH16.300m = 1% RH -55C
-60C70%RH18.000m = 1 RH -60C
RH means relative humidity in relation to water. Adjusted to "in realation to ice" by lowering the value by 10%
RH needed for cirrus forming at the given temperature. Actual altitude today, RH and temperature.
A newer one and more fine tuned:

Download the above picture and open it up in a picture viewer. Togle the frame to a smaller size. Now go there:
Atmospheric Soundings
Chose the observatory closest to you. Will open a new window. Look for a minimum temperature of -40Celsius ( minimum RH needed 90% ) and compare all other temperatures with the RH needed to form  cirrus clouds or persistent contrails. Better yet watch the sky. You see a newly made persistent contrail ( chemtrail ) ? Go to
#2 - Live flight tracker!  and check what plane was just flying over your place that made the chemtrail. Check altitude. Go to #1 and check for the altitudes temperature. Compare the temperature with #3  see above.
Relative Humidity and Temperature Influences on Cirrus Formation and Evolution: Observations from Wave

Clouds and FIRE II
Andrew J. Heymsfield and Larry M. Miloshevich

Mesoscale and Microscale Meteorology Division, National Center for Atmospheric Research, Boulder, Colorado
The wave cloud study extends analyses reported by Heymsfield and Miloshevich down to −56C, in part by using

an improved droplet size spectrometer with a detection threshold of 0.4 m am a Video Ice Particle Sampler

with a detection threshold of 5–10 m. The measurements show a rapid transition from solution droplets to

ice crystals characteristic of homogeneous ice nucleation throughout the temperature range from −35 to

−56C. The temperature dependence of the relative humidity and the droplet sizes when ice nucleation occurs

is consistent with theoretical and experimental expectations for homogeneous freezing. An expression is

given for the peak RH with respect to water in the wave clouds (RHhn), which decreases from 100% above −39C

to 73% at −56C; RHhn represents the condition required for ice nucleation in the wave clouds and is shown

to be more consistent with the homogeneous freezing of sulfuric acid solution droplets than ammonium sulfate

solution droplets.

Aircraft measurements made in cirrus during FIRE II show highly ice-supersaturated regions in clear air,

placing a lower bound on the RH required for cirrus formation approximately equal to (RHhn–10)%.

Measurements from a balloonborne Formvar ice crystal replicator are reported that show the vertical

structure of cirrus generally consists of three microphysically distinct regions: a highly ice-

supersaturated ice production region near cloud top, an ice-supersaturated ice crystal growth region, and a

sublimation region near cloud base formed by fallout of ice into ice-subsaturated air.
Heymsfield et al GRL 1998
Earlier findings are supported that RH,• in
mid-latitude, continental environments decreases from
water-saturation at temperatures above-39C to 75%
RH at-55C.
Uncertainty in determining RH,• below
-55C results in part from size detection limitations of
the microphysicailn strumentation, but analysis of data
from the SUCCESS experiment indicates that RH,•,•
below -55C is between 70 and 88%. A small amount
of data acquiredo ff-shores uggestst he possibilityt hat
RH,• may also depend on properties of the aerosols

"Andrew Heymsfield, Larry Miloshevich, and Steven
Aulenbach, along with Glen Sachse (NASA Langley) and
Sam Oltmans (NOAA) found that the relative humidities
with respect to water which are required to form ice
crystals in cirrus clouds decline from almost 100% near
40 degrees C to 75 or 80% from -55 to -65 degrees C.
This is consistent with their earlier measurements and
the notion of homogeneous nucleation of solution
droplets. But it is noteworthy that high relative
humidities, approaching 90%, were measured in clear air
at -52 degrees C off the coast of California and relative
humidities approaching 100% were observed in
orographic wave clouds between -62 and -65 degrees C.
These results indicate that very high relative humidities
can build up at low temperatures in instances with high
vertical velocities and possibly with depletion of cloud
condensation nuclei, thus retarding the formation of ice
crystals. These regions provide conditions highly
favorable for contrail formation by aircraft."

Posted by Clifford E Carnicom
August 4 2000

U.S. Naval Postgraduate School in Monterey CA and
Vincent Schaefer, inventor of cloud seeding in 1946,
both affirm that cloud formation is not expected to
even begin below relative humidities of 70%. That case
itself is considered unusual, exemplified with the
introduction of hygroscopic nuclei, such as salts in the
atmosphere along the coast. Persistent contrails
stated by numerous sources to have the potential to
exist only in conditions of near saturation to
saturation. Comments regarding relative humidity with
respect to ice are always welcome.
<saved as:quantitative-infrared-NASA in downloads>
Quantitative Infrared Spectroscop_y. o f Minor Constituents of
Earth’s Atmosphere
Charles Chackerian, Jr., Lawrence P. Giver
The observed rate of contrail spreading and maintenance
of optical depths larger than 0.1 can be
explained simply by the growth and precipitation of
ice crystals that nucleate during the initial contrail
formation if the environmental humidity is high
enough (relative humidity with respect to ice greater
than 125%)
. This result is consistent with the high
humidities observed in regions where the persistent
contrails formed on May 12. Also, the simulations
indicate that the humidity must be high throughout a
depth of at least several hundred meters below the
contrail to allow the crystals to continue growing as
they fall.
Point of Contact: E. Jensen