12 April 2007 Lidar Measurements of Atmospheric State Parameters in the Mesosphere and Lower Thermosphere Jonathan Friedman Arecibo Observatory Seminar 12 April 2007

Outline Atmospheric Structure Lidar Technique –Light Scattering –From photons to state parameters –Transmitter –Receiver (broadband/narrowband) Results –Ion-neutral interactions … sporadic layers –Mesospheric chemistry –MLT temperature measurements & solar influence

12 April 2007 Atmospheric Structure

12 April 2007 Light Scattering

12 April 2007 Total Receiver Efficiency No. of transmitted photons # of photons scattered from the atmosphere Probability that a scattered photon will be collected by the telescope Total Background photons Lidar Equation

12 April 2007 Blocking Detector Rayleigh Scatter Resonance Scatter 30 second average in 150 m bins Example of lidar data

12 April 2007 Rayleigh Temperatures in the upper stratosphere and mesosphere Assumptions The atmosphere is an ideal gas In hydrostatic equilibrium Assuming a starting temperature, T(z 1 ), integrate downward

12 April 2007 –Resonance Technique : Laser is tuned to the resonance wavelength of the atoms to be studied. –There is no signal if the laser is not on resonance with the target atoms. This allows us to map out the Doppler structure of the mesospheric metal atoms, both in terms of width (temperature) and shift (wind). –We know with fairly high accuracy, << 10 MHz in 400 THz, where in the spectrum the excitation laser is. 10 MHz is roughly equivalent to 7 m/s wind error and 1 K temperature error. Resonance Technique

12 April 2007 Transmitter & Receiver

12 April 2007 Daytime Receiver Typical filter 1/2 width ~ 1 nm. 1 pm 10 pm100 pm1 nm 100% 75% 25% 50% 0% Faraday Filter 1/2 width 1–10 pm

12 April 2007 Some Results 1.Summary of some past results Sporadic layers Metal layer seasonal structures Metal layer and meteors Temperatures, inversion layers, and Gravity Wave events 2.Recent scientific results on the seasonal thermal structure of the mesopause over Arecibo and its place in the global picture.

12 April 2007 Sporadic layer event during the 1998 Coquí II sounding rocket campaign

12 April 2007 Tepley et al., 2003

12 April 2007 Metal Layer Topside

12 April 2007 Temperatures and gravity waves

12 April 2007 Seasonal Climatology and how the mesopause above Arecibo fits into the global picture

12 April °N, Spitsbergen Höffner, 2006 Latitude Comparison 35°N, Albuquerque, NM (Starfire) Chu et al., °N, Arecibo, PR Friedman and Chu, °N, Maui, HI Friedman and Chu, 2006

12 April 2007 Radiative vs. Dynamic Heating/Cooling Radiative balance & upper mesosphere temperatures: - Coldest place on earth  winter polar mesopause - Warmest mesopause  summer pole - Tropical mesopause  nearly isothermal In fact: - Coldest place on earth  summer polar mesopause Under constant sunlight! - Warmest mesopause  equinox - Tropical mesopause  structured and dynamic Does not explain the summer cold tropical lower thermosphere

12 April tidal oscillations a work in progress

12 April 2007 January Analysis

12 April h tide at 95 km Dusk Dawn Midnight

12 April 2007 Summary Lidar allows us to make remote measurements of the “ignorosphere” with high time and range resolution. Takes advantage of a high-intensity coherent source and an inefficient but reliable tracer to probe atmospheric state parameters. Allows us to study a variety of phenomena in the middle atmosphere.