SHIMMER successfully observes Earth's highest clouds

Nov 13, 2008
Number of PMCs observed by SHIMMER between 50-58°N versus local time. The red line (2007) shows a clear semidiurnal behavior, whereas the black line (2008) illustrates that in 2008 diurnal behavior is observed. How this difference in cloud occurrence is related to other meteorological data, such as winds and temperatures, is subject to ongoing and proposed work. Credit: Naval Research Laboratory

The Naval Research Laboratory's Spatial Heterodyne Imager for Mesospheric Radicals (SHIMMER) has successfully observed a second northern season of Polar Mesospheric Clouds (PMCs), which are the Earth's highest clouds. This successful observation fulfills the primary goal of the Space Test Program Satellite-1 (STPSat-1) Extended Mission.

SHIMMER was originally launched as the primary payload of STPSat-1 on March 8, 2007, with the objective to demonstrate the novel optical technique of Spatial Heterodyne Spectroscopy and to obtain global measurements of the hydroxyl (OH) radical in the Earth's mesosphere (50-90 km altitude). After the successful completion of its nominal 1-year mission, STPSat-1 operations were transitioned to NRL, which has been operating the spacecraft since June 1, 2008 using a novel, low cost operations approach.

The primary objective of the SHIMMER Extended Mission was to continue global scale PMC observations during the northern PMC season, which ended in August 2008. PMCs form in a thin layer in summer near 82 km over polar latitudes. Some have argued that, due to increases in atmospheric humidity, cloud occurrences have been increasing in recent decades. Because STPSat-1 is in a relatively low inclination orbit, SHIMMER observes PMCs at their equator-ward edge (<58°), but more importantly, makes measurements at a wide range of local times. This ability for SHIMMER to make measurements of the variation of PMCs throughout the day is unique among the several satellites that have observed PMCs, explains Dr. Christoph R. Englert, principal investigator of SHIMMER.

SHIMMER has now measured the PMC diurnal variation for the two northern seasons of 2007 and 2008, and surprisingly, the variation is quite different. Even though a semidiurnal signature, that is two peaks per day -- one in early morning and one in the late afternoon -- was observed in 2007; in 2008, the variation was diurnal or one peak per day (see figure). This result has important implications for the inference of long-term trends from historical, space-based PMC observations because NASA and NOAA satellites that have observed PMCs over the last 25 years have all been launched into sun-synchronous orbits with different, fixed local times. Until the diurnal variation of these clouds is better understood, the SHIMMER data show that it is premature to make firm conclusions about multi-decadal trends in PMCs.

Source: Naval Research Laboratory

Explore further: New study confirms water vapor as global warming amplifier

add to favorites email to friend print save as pdf

Related Stories

T-Mobile deal helps Rhapsody hit 2M paying subs

46 minutes ago

(AP)—Rhapsody International Inc. said Tuesday its partnership with T-Mobile US Inc. has helped boost its number of paying subscribers to more than 2 million, up from 1.7 million in April.

Airbnb woos business travelers

58 minutes ago

Airbnb on Monday set out to woo business travelers to its service that lets people turn unused rooms in homes into de facto hotel space.

Recommended for you

Huge waves measured for first time in Arctic Ocean

3 hours ago

As the climate warms and sea ice retreats, the North is changing. An ice-covered expanse now has a season of increasingly open water which is predicted to extend across the whole Arctic Ocean before the middle ...

New research reveals Pele is powerful, even in the sky

9 hours ago

One might assume that a tropical storm moving through volcanic smog (vog) would sweep up the tainted air and march on, unchanged. However, a recent study from atmospheric scientists at the University of Hawai'i ...

Image: Wildfires continue near Yellowknife, Canada

9 hours ago

The wildfires that have been plaguing the Northern Territories in Canada and have sent smoke drifting down to the Great Lakes in the U.S. continue on. NASA's Aqua satellite collected this natural-color image ...

Excavated ship traced to Colonial-era Philadelphia

10 hours ago

Four years ago this month, archeologists monitoring the excavation of the former World Trade Center site uncovered a ghostly surprise: the bones of an ancient sailing ship. Tree-ring scientists at Columbia ...

User comments : 0