First we have to assume that the planet's spin direction and orbital tilt are the same as Earth's. I would not assume Himalayan heights...the Himalayas are abnormally tall for mountains on earth, caused by a massive high speed plate collision that I don't see any evidence for in your map. Most mountain ranges probably topped out in the 4000m-6000m range through earth's history. Lets say your dark region in the Lesser Southlands is a ~4000m plateau surrounded by peaks up to 6000m, like the Altiplano of Peru and Bolivia.
Currents
You have a landmass that is completely exposed to the effect on oncoming currents on both coasts, so those currents will probably dominate the climate. The west coast of continents generally sees cold currents from the poles heading towards the equator (such as the California, Peru, Benguela, and Canary currents). The east coast will see warm currents from the equator to the poles (Agulhas, Gulf Stream, Brazil).
The climates that on West Coast go from Rainforest to Cool Desert to Mediterranean to Temperate Rainforest to Arctic. North America, South America, Africa/Europe, and the southern half of Africa all follow this pattern (though South Africa runs out of land in the Med zone).
The Climate son the East coast tend to go Rainforest, Wet/Dry Savannah, Humid Subtropical, Humid Cold-Winter, then Arctic. East Coast of North America is the best example. East Asia follows the patten, but has an additional monsoon bringing heavy summer rains, which I'll get into below. South America mostly follows the pattern, but doesn't have a large landmass to get the polar cold winters, after the Humid Pampas near Buenos Aires, it goes into cold dry Patagonia. Your continent would probably be this version look like this.
Atmospheric Movement
Another pattern that affect the earth is the Intertropical Convergence Zone (ICZ). This is a band of heavy rainfall that moves to the Tropic of Cancer (North) during the northern summer and to the Tropic of Capricorn in the southern summer.
Prevailing winds between the tropic and equator are westerly and towards the equator, prevailing winds between the tropics and arctic/antarctic circle are easterly and towards the poles.
Humid air tends to rise at the equator causing rainfall and dry air from high altitudes tends to descend around the tropics and cause reduced rainfall. This is the reason that the equator is blanketed in rainforest, but the tropics tend to go through deserts.
Monsoons are caused by proximity of an ocean to a land mass that will heat up and cool down much faster than the ocean. The three major Monsoon systems of earth are caused by the Sahara Desert (West African Monsoon), Tibetan Plateau (Indian Monsoon) and Siberia (East Asian Monsoon). I don't see anything large enough on your map to cause a true monsoon. Maybe some weak smi-reversing monsoons, as we'll see below.
Arctic Regions
The North Pole of earth is completely surrounded by land and acts almost like a lake. The South Pole is a continent surrounded by water which is isolated by a strong circumpolar current. Your world has neither feature, so I'm not exactly sure what would happen. I'm going to assume that permanant pack ice never reaches the continents. Winter feature strong, constant, cold south-blowing winds from the poles to 60degrees latitude. Summer features a mild poleward breeze. The poles are over water, not land, so you can't get the frigid air masses that form over Siberia or Canada. Your land masses probably never get down to -20F. A comparable situation is Trondheim, Norway, on the Arctic circle with no land north of it, the record low is -14.8C.
Summary of Regions
- North and West Northland (NOTE: NEED BETTER CONTINENT NAMES) are subarctic to temperate rainforest (Norway)
- Northwest Westland is Mediterranean (Spain), Central-west Westland turns to Dry Desert (Morocco).
- South Westland is tropical savannah turning to rainforest, with cloud forests on top of the mountains (like Thailand/Indochina).
- The islands between Westland and Greater Southland are rainforest.
- Northwest Greater Southland is dry savannah turning to semi-desert scrub and desert (like the Sahel of Africa). This is the largest desert in your map. The region trapped by mountains on three sides in the heart of the continent is a big sea of sand.
- South Greater Southland is cool temperate forest, like European Russia.
- The island below Lesser Southlands are Mediterranean like Perth, Australia (this is because of the cold circumpolar current coming below Greater Southlands). Best fisheries on the planet.
- The eastern side of the south coast of Lesser Southlands have a wet oceanic climate, like Sydney and Melbourne Australia. As you go west, and higher in altitude, the rain drop off quickly. On the coast the weather will be like Adelaide, Australia at higher altitudes you get a dry climate like the Karoo of South Africa.
- Southeast Eastland is the biggest rainforest on your planet.
- The central and eastern parts of Westland (inside the ring of mountains) are are dry 6-8 months of the year, and then have brief wet season brought by the ICZ, but much of the water is blocked by mountains to the south. Semi-desert scrub mixes with dry thorn forest like the Deccan Plateau in India. Against the southern mountains you get heavy rainfall as the ICZ retreats in fall, so there you get a wetter seasonal forest. Probably the best place in your planet for big safari animals.
- The basin of North Eastland, South Northland, and Northwest Westland is a steppe, and the biggest set of grasslands on your planet. The climate is like the Black Sea basin...except this is much larger and stretches much farther north to south. The south would start to be hot and dry like Phoenix, while the north will grade into forest-steppe like Kiev, Ukraine. Best agricultural area on the planet.
