MET 61 1 MET 61 Introduction to Meteorology MET 61 Introduction to Meteorology - Lecture 9 “Radiative Transfer” Dr. Eugene Cordero Stull: Chapter 2 Class Outline: Solar elevation and azimuth Surface radiation budget

MET 61 2 MET 61 Introduction to Meteorology Activity question Question 3: Calculate the radiative equilibrium temperature of the Earth’s surface and Earth’s atmosphere assuming that the earth’s atmosphere can be regarded as a thin layer with an absorptivity of 0.1 for solar radiation and 0.8 for terrestrial radiation. Assume the earth’s surface radiates as a blackbody at all wavelengths.

MET 61 3 MET 61 Introduction to Meteorology

MET 61 4 MET 61 Introduction to Meteorology

MET 61 5 MET 61 Introduction to Meteorology Nomenclature Earth’s tilt relative to orbital plane:  r =23.5° Solar declination angle (angle between ecliptic and equator):  s Julian day: d (day number ) Local elevation angle:  (sun angle relative to horizon) Solar zenith angle:  (sun angle relative to the vertical) Azimuth angle (sun angle relative to north)

MET 61 6 MET 61 Introduction to Meteorology Solar declination angle The solar declination angle is a function of the day of the year. C=2  (360°); d r =173 (summer solstice); d y =365 (or 366 if leap year)

MET 61 7 MET 61 Introduction to Meteorology Solar declination angle The solar declination angle is a function of the day of the year. C=2  (360°); d r =173 (summer solstice); d y =365 (or 366 if leap year)

MET 61 8 MET 61 Introduction to Meteorology Local Elevation Angle The local elevation angle is a function of the day the year and local time (ranges from 0-90°)  =latitude;  s =solar declination; C=2  (or 360); t d =length of day; t UTC =time of day in universal time; e =longitude (positive west of Greenwich meridian;

MET 61 9 MET 61 Introduction to Meteorology Local Elevation Angle The local elevation angle is a function of the day the year and local time (ranges from 0-90°)  =latitude;  s =solar declination; C=2  (or 360); t d =length of day; t UTC =time of day in universal time; e =longitude (positive west of Greenwich meridian;

MET MET 61 Introduction to Meteorology Local Azimuth Angle The local azimuth angle is a function of the day of the year and local time. (ranges from 0°-360 °)  =latitude;  s =solar declination;  =C/4-  (  =C-  if afternoon); C= 2  (or 360)

MET MET 61 Introduction to Meteorology Local Azimuth Angle The local azimuth angle is a function of the day of the year and local time. (ranges from 0°-360 °)  =latitude;  s =solar declination;  =C/4-  (  =C-  if afternoon); C= 2  (or 360)

MET MET 61 Introduction to Meteorology Surface Radiation Budget The net radiative flux perpendicular to the earth’s surface is

MET MET 61 Introduction to Meteorology Surface Radiation Budget The net radiative flux perpendicular to the earth’s surface is

MET MET 61 Introduction to Meteorology Surface Radiation Budget (II) The longwave IR is

MET MET 61 Introduction to Meteorology Surface Radiation Budget (II) The longwave IR is

MET MET 61 Introduction to Meteorology

Simplified radiative energy cascade for the Earth-atmosphere climate system Energy Input Energy Output E-A Climate System Extraterrestrial Short Wave Radiation Reflected Extraterrestrial Short Wave Radiation Terrestrial Long Wave Radiation Planetary Albedo Solar Temperature Planetary Temperature

MET MET 61 Introduction to Meteorology Activity 8 (Due April 4 th ) Question 1: Determine the local elevation and azimuth angle at SJSU for March 25 th, 2007 at noon local time. Verify this visually if possible! Question 2: Estimate the net radiation at the surface of SJSU (assume some albedo and justify) at the above time assuming two conditions: –A) Low clouds are present with a 50% coverage –B) No clouds are present. Question 3: Plot out the solar elevation angle versus the local time for Jan 20 th, March 20 th and June 20 th over San Jose. Explain your results. Question 4: Plot out the local elevation angle at SJSU at noon for an entire year. Explain your results.

MET MET 61 Introduction to Meteorology Quiz 1 Tuesday, Feb 24: ~ 30 minutes Part I: Multiple Choice/Short Answers –From Ahrens reading; general concepts –Closed book (notes) Part II: Problems –Like activities –Open book (notes)

MET MET 61 Introduction to Meteorology Review questions On June 21 st, at what latitude is the sun directly overhead at noon? On September 22 nd, at what latitude is the sun directly overhead at noon? How many hours of daylight are present at the South Pole on February 20 th ? Where would you expect to have longer days; 45 ° N on June 21 st or 50°S on Dec 21 st ?