Thursday, March 29, 2018

Heat sea and air to bring rain

Cape farmers were having trouble with frost and now there are problems with drought.
There are two things needed for convectional rain and those are 1) Moisture in the air 2) Upward convection of air. As to moisture you can place black sheeting in the sea off Cape Town to heat the sea and supply moisture - see
https://airartist.blogspot.co.za/2018/03/could-we-create-small-el-nino-close-to.html

As to convection, you could have tall poles with rigid black plastic "roofs" on to shade crops and heat up the air above the black plastic (which will get hot in the sun). The black plastic will work in an opposite way to "cool roofs" which reduce rainfall - see https://www.scientificamerican.com/article/cool-roofs-may-have-side-effects-on-regional-rainfall/

As to frost (winter is coming), have sheets of plastic, on the poles mentioned, that deflect wind downwards and keep mixing warm air into the cold air near the ground.

Saturday, March 24, 2018

Rain with biological heating simulation

Could we create a small El Nino close to Cape Town with black plastic sheets?  I have been reading some articles on the formation of El Nino and Wikipedia at  https://en.wikipedia.org/wiki/Mixed_layer says, "The depth of the mixed layer is thus very important for determining the temperature range in oceanic and coastal regions. In addition, the heat stored within the oceanic mixed layer provides a source for heat that drives global variability such as El NiƱo." 
Now another article says that chlorophyll causes the solar energy to be captured in the top layer of ocean and, despite strong winds, a shallow mixed layer of warm water 20 to 30 m deep persists on top of the ocean where there is chlorophyll (biological heating of the surface) - see 
https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2003JC002024 
I therefore maintain that my cheap black floating plastic sheets will keep a warm layer on top (simulating biological heating) and will enhance rainfall. Probably for 10 million rands or so one could have a huge grid of floating black plastic sheets, say 50 m apart, that would enhance rainfall.
Reminder of my black floating plastic sheets idea: 
Hot water floats on cooler seawater and does not mix easily. For rain enhancement have cheap rigid black plastic sheets with plastic floats on the side that allow the black sheet to remain a few centimetres below the water surface Have a hole in the middle of the rigid sheet to let seawater in and out slowly. The black plastic sheet will absorb the visible light energy and infrared from the sun and when it radiates heat the heat radiated will be in the infrared range ranging around about 10 microns or so in wavelength. That type of radiation is absorbed within mm of penetration of sea, so in effect you have a greenhouse heating up with solar energy, because a few mm of seawater above the sheet will not allow radiation to exit the sea. http://www1.lsbu.ac.uk/water/water_vibrational_spectrum.html tells us that absorption coefficients are around 1000 per cm for this situation. This means that the intensity of radiation from the black sheet will drop to 1% of its original intensity within 0.046 mm of penetration of the seawater above it.
The floating hot water will humidify and heat the air above it. This more humid less and dense air will rise increasing chances of convectional rain. These black sheets could float like so many boats on the sea outside drought areas. With 7 kWh of solar energy per square metre per day falling the black sheets could heat water above them, that is 1 m deep, by 6 deg C in a day.
https://journals.ametsoc.org/doi/full/10.1175/1520-0442(2004)017<1097:BHITEP>2.0.CO%3B2
​ also has interesting information about biological heating.


Tuesday, March 6, 2018

Cooling cities and enhancing convectional rain

Method to cool hot cities, decrease air pollution and bring convectional rain. How does a city get hot? Well the sun shines on outside walls of buildings and the walls heat up and radiate heat to all objects around. How could you stop this? If you place greenhouse plastic, on the outside of buildings, a few centimetres away from the walls, then the sun shines (with high frequency radiation from the hot sun) through the greenhouse plastic onto the walls which heat up. Now the low frequency infrared radiation from the hotter walls (cooler than the sun) cannot get out through the greenhouse plastic and so will not heat up people and other objects around the walls. Instead the air is heated up between walls and greenhouse plastic and convection causes it to rise. The walls thus become air-cooled and the heat is transferred to the air. The rising air will draw in cleaner air from the air surrounding the city, the chances of convectional rain will be increased (more than just from having the urban heat island effect) and the city could become cooler because of:
1) Virtually no infrared radiation from hot walls of buildings onto objects. There will be some radiation from the greenhouse sheeting, but sun shines through greenhouse sheeting without heating it much at all.
2) Air cooling
There will also be possible cooling from:
1) Cloud formation that will shade the city
2) Rain which cools.

Thursday, March 1, 2018

Simulating convergence of moist air masses.

Many parts of the world are experiencing water shortage. If one could use rain enhancement to grow plants in the desert and soak up carbon dioxide it could help reduce global warming and drought. After I sent out an idea on rain enhancement to the Australian Water Association they suggested I submit a paper of about 5000 words to them on it, so perhaps they see merit in the idea. The idea depends on the principle of narrow land masses that heat up during the day, causing air to converge from both sides, meet in the middle, and rise because of high pressure where they collide. Imagine high walls running parallel, about a kilometre apart that cross the narrow land mass. Now bend the parallel walls into a U with ends facing the most windy direction. The pressure at the U part will be high, simulating convergence of air. Place dark biochar on the ground between the walls so it heats up and heats the air. This U shaped apparatus could be built in areas like Cape Town where it is windy and it will simulate places like Florida where convergence causes heavy rain. It could be built cheaply with tall poles with fabric stretched between the poles. Sea breezes often have depth of only 300 metres or so, so 300 m high walls may suffice.
There is advantage with convergence of air masses over the usual sea breeze. With a sea breeze the cooler air from the sea lifts the drier hotter land air and when the drier land air rises clouds and rain can occur. With convergence of sea breezes moist sea air is forced to rise and the more moist air facilitates rain.


Wednesday, January 31, 2018

If coastal cities need more rain...

Can also visit https://www.facebook.com/groups/RainSeaVsAirT/
If coastal cities need more rain they could try heating water in greenhouses to add water vapour to the air. Here is a graph (below) using the average of six evaporation equations. You can get 20 or more times the evaporation by increasing water temperatures. 
Studies on evaporation from windy sea conditions show more rain with more evaporation of spray. 
In many cities you can evaporate over 100 000 litres every day with a 100m by 100m greenhouse and add it to the atmosphere, humidifying it and increasing chances of rain. 1kWh can evaporate about 1.5 litres and many cities can easily get about 8 kWh of solar energy on every horizontal square metre in a day.
When the air is hotter than the sea the water cools the air immediately above it and the relative humidity (RH) of this air increases and water can even condense out of the air so that "negative evaporation" occurs. If the seawater is hotter than the air the evaporation increases substantially, because the water heats the air above it, the RH of the air decreases, and the hotter air can take up moisture faster. This principle of high evaporation rate with water being hotter than air can be used to increase the humidity of the air and increase chances of rainfall. Therefore, heating seawater in greenhouses and so on can be very effective. Evaporation equations do not all give the same rate of evaporation and I use an average from six evaporation equations. Example: Wind speed=10 km/h, Air temperature above water is 32 deg C, temperature of water is 20 deg C, pressure = 1 atm. The average of the six equations is -1 mm per day so water condenses out and we could get a mist immediately above the water. Now we keep everything the same except we heat the water in a greenhouse to 37 deg C. The rate of evaporation (given by the average result of the 6 equations) is now 28 mm per day and we can increase the humidity of the air substantially, increasing chances of rain. Calculations show, if the area of greenhouses were one square kilometre, one could evaporate over 10 million litres a day in sunny areas.

Air tends to move back and forth with sea breezes and land breezes, so the humidity could accumulate every day from the greenhouse evaporation.
 BELOW IS A GRAPH SHOWING HOW EVAPORATION FROM THE SEA CAN BE INCREASED BY HEATING SEAWATER. INCREASED EVAPORATION MEANS INCREASED CHANCES OF RAIN:

Here is another graph (below) where air temperature is increased by only 1 deg C. So, as the air heats more relative to the sea, so the evaporation from the sea decreases. Decreased evaporation means decreased chances of rain.




Tuesday, January 9, 2018

Rain by humidification above the ocean.

Above shark nets, about 20 m above the ocean, have thick pipes with thousands of holes in that water streams out. Water can be pumped into the pipes using wind turbines. If the wind is blowing at 10 km per hour and the pipes are 1 km long, then the volume of air humidified in an hour is 1 km x 10 km x 0.02 km = 0.2 cubic kilometres.
In a day this is 4.8 cubic km of air. Nights are warmer with more humid air and I am going to use this as an example: RH=65% and Tair=20 deg C before humidification. RH=80% and Tair=22 deg C after humidification (the air will be blowing back and forth with land and sea breezes). Before humidification the water vapour content of the air is 11.2 grams/cubic metre and after humidification it is 15.5 grams/cubic metre. This is an increase of 38%. This relies on the fact that more humid air will keep in heat from the ocean when air is colder than the ocean. See 
http://www.asterism.org/tutorials/tut37%20Radiative%20Cooling.pdf

The heat from the ocean will help humidify. Air is usually colder than the ocean at night. During the day any mist will absorb solar energy and heat up and evaporation will occur. 

Thursday, January 4, 2018

Easy wet bulb temperature determination

People have been searching on the Internet for an easy way to calculate wet bulb temperature (and so have I). Experts give various long calculations and I wanted an accurate value easily calculated. I had a lot of trouble searching on various forums and eventually found a site that uses an equation that can be solved numerically that gives me an accurate answer, but the formula did not work unless I changed the P units from hectopascals to atmospheres. So instead of 1000 hPa I use 1000/1013.25. I solve numerically using a computer program I wrote to get Tw (wet bulb temperature). The formula is at
and I notice that P is included in one equation and left out in the next equation. However if you use atm it should work well with P included in both. The formula gives RH, but you can find Tw numerically. Say you are trying to find the wet bulb temperature for Td=45 deg C and RH=67%. Then let RHS=formula given and start with Tw=45 (represents RH=100%) and decrease Tw iteratively until RHS<=67. Find Tw at that point.

You can use a wet bulb calculator to check how accurate the above formula is (pretty good).
Your inputs into the program will be Td, RH and P. (P in atm). (Td is dry bulb T and Tw is wet bulb T.)

Code in Pascal:
Tw:=Td;
repeat
Tw:=Tw-0.001;
A:=611.2*exp(17.502*Tw/(240.97+Tw))-66.8745*(1+0.00115*Tw)*P*(Td-Tw);
B:=6.112*exp(17.502*Td/(240.97+Td));
RHS:=A/B;
until (RHS<=rh);

{Now print Tw}