Its measurement and variation over the last 50 years Ralph Markson 2007 February 23 2017 Karly Reimel ATS 780 Why do we want to measure global circuit intensity There is a possibility that monitoring the global circuit could be a tool to monitor global temperature change ID: 584753
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Slide1
The Global Circuit Intensity: Its measurement and variation over the last 50 years
Ralph
Markson
(2007)
February 23, 2017
Karly Reimel
ATS 780Slide2
Why do we want to measure global circuit intensity?
There is a possibility that monitoring the global circuit could be a tool to monitor global temperature change
The intensity of the global circuit can be measured with a single measurement
Convective clouds are modulated by heating of the Earth’s surfaceConvective clouds maintain the global circuit and associated fair weather fieldIonospheric potential (Vi) is proportional to the intensity and variation of Earth’s electric field.Measuring global circuit intensityConstant altitude time series measurements of electric field or air-Earth current over a diurnal cycle at remote fair weather locations with few or no clouds above or below the measurementTime series of Vi soundings over a full day or substantial portion of the daySimultaneous measurements of Vi at remote locationsSlide3
Soundings of ViShould be taken in clean-air ocean regions with no clouds or only scattered cloudsElectric field decreases quasi-exponentially with height, so soundings do not need to reach high altitudes
Potential difference between the ground and sounding top is measured directly
The remainder of the sounding can be extrapolated since the variation of the electric field with altitude has a known exponential decrease with altitude above the lower atmosphere
Add the integrated potential to the computed increment to get ViOcean Aircraft Sounding:E= electric field soundingV= integrated potential variation with heightExchange layer occurs at 1.4kmConductivity rapidly increases since aerosol are confined to the boundary layerExponential decrease in E due to the increase in cosmic ray ionization with altitude
(
Markson
2007)Slide4
Balloon Sounding:
Taken in clean air in Hawaii
Unusual electrode space charge layer near the ground
Inversion at 1km followed by the characteristic exponential decrease in EEnhanced E near 3km most likely due to a thin cloud layer that creates lower conductivityThe Electrode Layer:a layer of positive space charge near the surfaceAlways observed over the ocean but rarely observed over landCaused by accumulation of positive ions drifting downward in the fair-weather electric fieldElectrode layers are uncommon over land because Earth’s land surface contains uranium and radon which both ionize air molecules close to the groundSince Hawaii is volcanic, there is no uranium or radon in the ground(
Markson
2007)Slide5
Variation of Ionospheric Potential (1955 – 2004)
Aircraft and balloon soundings of Vi were completed by multiple groups over a 50 year time span
Soundings were normalized to account for the diurnal variation in Vi
The Carnegie curve percent deviation from its mean value was added or subtracted from the measured Vi depending on the time of the measurementVi measurements averaged for each yearAtmospheric Nuclear TestingAfter WWII, atmospheric nuclear testing occurred from the 1950’s through 1962The frequency in this testing rose significantly just before the test ban treaty went into effect in 1963
Average of all years: 254kV
Average after 1966: 240kV
(Markson2007)Slide6
Ground Level SR-90
Stratospheric SR-90
Correlations between Vi and SR-90
Both ground level and stratospheric SR-90 showed the highest correlation with a lag time of 1 year
On average it takes 1 year for nuclear fallout to reach the ground or settle in the troposphere when it originates from the stratosphere
Stratospheric SR-90 shows a higher correlation to variation in Vi than ground based SR-90 measurements
Effects of Nuclear Testing on Vi
Nuclear material in the stratosphere is a better measure of the ionization in the upper troposphere that could affect the conductivity above thunderstorms and their ability to maintain the global circuit
Nuclear fallout near the ground causes enhanced ionization that leads to an increase in conductivity
The enhancement of Vi by as much as 40% from 1960-1965 was caused by nuclear radiation in the upper troposphere and lower stratosphere
(
Markson
2007)Slide7
Cosmic Radiation and the Global Circuit
Previous studies have found:
Negative correlation between solar wind velocity and Vi
(Markson and Muir 1980)Positive correlation between galactic cosmic radiation and Vi (Markson 1981)Solar wind velocity is inversely correlated with cosmic radiationConclude that cosmic ionizing radiation must increase Vi by affecting the generator part of the circuitMarkson 2007 supports this conclusion through finding that atmospheric nuclear radiation is positively correlated with ViNuclear radiation enhances ionization in the same way as cosmic radiation would(Markson
1981)Slide8
(
Markson
2007)
Annual Variation of ViRelatively constant Vi over timeApproximately a 10% increase occurs moving toward a maximum in AugustVi values level out in September and October and then decreases back down to its quasi-stable valueUnable to identify a month that represents the minimum value, but the winter months appear to have the lowest values of ViSlide9
A study of the relationship between Vi and temperatureCompared Vi measurements from balloon soundings in Weston, Massachusetts to high temporal resolution temperature data in equatorial and tropical Africa and South America
Found significant positive correlations between the temperatures between
and analysis of the balloon soundings
Over Africa, the correlation maximized when the temperature 5 hours before the sounding was usedCorrelation maximized 2 hours before the sounding in South AmericaA similar experiment was completed using 19 balloon soundings over Orlando, FloridaDemonstrated that temperature controls Vi variationShowed that a negative feedback mechanism exists
High positive correlation in the morning
High negative correlation in the midafternoon through evening
Morning and midday convective development leads to the overdevelopment of clouds, reduced temperature due to shading, and minimal thermal activity later
(
Markson
2007)Slide10
Warmer noontime temperatures lead to smaller increases in temperature in the midafternoon
Earlier convection due to warmer noontime temperatures increases cloud cover, reducing the heating of the surface through longwave radiation
On a diurnal time scale, this relationship should stabilize temperatures
On a longer time scale, a positive feedback should result from increased thunderstorm activity adding more water vapor to the air(Markson 2007)Slide11
(Price 2000)
Deep Convective Clouds and Global Warming
Most of the reported global warming signal comes from warmer nighttime temperatures
Residue clouds and water vapor from daytime thunderstorms and deep convection inhibit nighttime radiational coolingDeep convection transports water vapor to higher altitudes where it is much more effective as a greenhouse gas than at the surfaceELF/Schumann resonances are highly correlated with water vapor in the upper troposphereIncreased convective activity should increase nighttime temperatures and contribute to the global warming signalSlide12
Sensitivity of Vi to temperature
An 8
C increase in temperature corresponds to 100-kV increase in Vi
A 1% increase in temperature results in a 16% increase in Earth’s electric field intensityGlobal Warming ImplicationsIt is not possible to compare the long-term variation of Vi to global warming due to the ratio of Vi to temperatureThe reported 0.4C increase in global temperature over the past four decades would coincide with a only a 4kV increase in ViPerhaps with the further refinement of measurements in the future, Vi variation may provide a relatively simple method to study global change
(
Markson
2007)Slide13
Conclusions:Atmospheric nuclear testing was highly correlated with an increase in global circuit intensity by as much as 40% from 1960-1964
Following the nuclear test period, Vi has remained relatively constant, averaging about 240kV
Positive correlation between atmospheric nuclear radiation and Vi supports the hypothesis that galactic cosmic radiation modulates the intensity of the global circuit through changing the ionization properties near deep convective clouds
The maximum variation of Vi and annual variation observed of lightning occurs in August; the minimum in Vi occurs during Northern Hemisphere winterSlide14
Conclusions:Temperature over Africa and South America are positively correlated with Vi in the morning and negatively correlated in the afternoon– most likely due to enhanced morning convection creating clouds that shield the ground from solar radiation later in the day
Convection transports water vapor to the upper troposphere and stratosphere– contributes to global warming signal due to water vapor acting as a greenhouse gas
Nocturnal clouds and water vapor from previous day’s convection reduce the rate of radiational cooling at night
A 1% change in global temperature leads to a 16% change in Vi– currently the temperature change is too small to notice a variance in Vi, but with further refined measurements, Vi could provide a method to study global change one day